Ask a room of very experienced animal behaviorists what “mlem” means and you will get a beat of silence, followed by some polite confusion. A certified cat behavior consultant will tell you honestly that he is not sure. A dog behavior expert with nearly two decades of experience will ask you what it is. Another feline consultant will admit he had to look it up, and that his first round of searching returned nothing but videos about lemmings.
That is your first clue.
Mlem is not a behavior. It is a noise, and specifically it is an internet word for a noise. What it labels is the small wet sound produced when a dog or a cat runs their tongue over something, most often their own muzzle: the nose, the lips, the teeth, the gums. It looks vaguely like corn-on-the-cob eating. It is enormously cute. And the meme economy has absorbed it as shorthand for an animal who is happy, loose, and a little bit silly.
And that framing is the problem. Because the sound means nothing at all, while the lick producing it is one of the more reliable distress signals in the canine and feline repertoire, and an entire generation of pet owners has been trained by their feeds to read it as bliss.
Where the word came from, briefly
It is an onomatopoeia, a word that imitates the sound it names, and it is genuinely new. It first appeared on Urban Dictionary in 2015 and made it into Dictionary.com’s slang compendium in 2019. The earliest recorded use appears to be a meme posted to Imgur and Reddit in February 2015. It is also said to imitate the noise Yoshi makes when he sticks out his tongue after Mario whacks him in the back of the head in 1990’s Super Mario World.
Onomatopoeia is deeply personal and does not survive translation, which is half the reason nobody agrees on it. Ask an Italian speaker what a dog says and you will hear “bau bau,” not “woof.” A Russian speaker will say “gav.” A Korean speaker, “meong.” One of the behaviorists consulted here said he would personally call the noise a “shlerp,” which, honestly, is at least as good.
The point is that “mlem” is a piece of internet vocabulary, not a piece of animal communication. The consultants are united on this. Nothing is being intended by it. Unlike a hiss, or a meow, it is not addressed to anyone; it issues no warning and extends no invitation. It is a byproduct, and largely an involuntary one, of a tongue moving.
Now the part that matters
Strip away the noise and look at what the animal’s tongue is actually doing.
In dogs, a lip-lick is a stress signal. Not always, and context is everything, but it sits in a well-documented family of appeasement and displacement behaviors that includes yawning, turning the head away, and whale-eye. A dog who licks their lips while being hugged, while a stranger leans over them, while a toddler approaches, is not savoring anything. They are managing discomfort.
Cats run a similar system. A nose-lick in a cat is frequently a displacement behavior, which is the technical name for a feline fidget: an action performed to bleed off tension rather than to accomplish anything. It might equally be tooth-cleaning, or the aftermath of something tasty. Context decides.
Which produces a genuinely unfortunate collision. The exact frame that reads as contented pet in a meme is, in a lot of real-world footage, a stressed pet asking for space.
“The lip-lick is one of the first things I teach people to see, and it is the one they resist hardest, because the internet has taught them it means the animal is happy,” says Dr. Nina Kohl. “A dog licking their lips while a child hugs them is not enjoying the hug. That is the dog being polite. And politeness is a resource that runs out.”
There is a practical rule inside this, and it is the most useful thing on this page:
About to greet an unfamiliar dog or cat, and their tongue keeps flicking over their lips? Don’t. A cue that quiet still deserves to be honored as a request for room. That goes double where children are concerned, since a child will walk straight up to a “smiling, licking” dog with absolute confidence.
The other reason it is misread: it looks like relaxation, and sometimes it is
To be fair to the memes, the behavior is genuinely ambiguous, and pretending otherwise would be its own error.
Read the wrong way, a chop-lick will tell you a dog is anxious. Read the right way, in a different body and a different room, the very same movement belongs to a dog who is powering down and settling, which is more or less the version the memes are showing you. Both readings are legitimate. Which is precisely why no rule survives without a look at the entire animal.
So look at the entire animal. A lick paired with a loose, wiggling body, soft eyes, and an easy open mouth is one creature. A lick paired with a rigid frame, a tucked tail, a head swiveled away, hard eyes, or a yawn is a different creature entirely. And in dogs, a lick of the lips plus a yawn plus a sudden inspection of their own genitals, sometimes called a urogenital checkout, is a stress cluster, not a coincidence.
The signal is not the lick. The signal is the combination.
When licking becomes a medical question
Everything above is about a lick or two in a moment. The other axis is volume, and that one is a health issue.
The key word is excessive. An animal producing that noise on a loop, morning to night, has stopped making a comment and started reporting a problem.
In cats. Excessive grooming is often a sign of an underlying medical problem. Left unaddressed, it can progress to psychogenic alopecia, thinning or bald patches driven by over-grooming. It can also be a response to serious disease the owner has no idea about. One consultant describes a cat who began licking excessively toward the end of his life, staining his white fur brown, and was subsequently diagnosed with cancer. That is not offered to frighten anyone. It is offered because the licking was the first visible thing, and it was visible for a while.
And the broad feline rule stands behind all of it: when a cat’s behavior shifts abruptly, and especially when several things shift at once, that cat belongs in front of a veterinarian. Heavy licking driven by stress or discomfort that nobody ever gets to the bottom of has a way of leaking sideways, too, into aggression, into the litter box, into a dozen other problems you did not sign up for.
In dogs. Licking one spot on the body over and over frequently means allergies. It can also mean pain in the joint underneath the spot they will not leave alone, which is why a vet may want an X-ray of a leg the dog has been licking raw.
Surface licking in dogs, meaning the floor, the carpet, the couch, deserves its own note. It can be innocent: they enjoy the taste, or they are interrogating a spot for information that the nose and eyes could not fully extract. Once it turns repetitive, the list of explanations gets worse. It can point to boredom. It can point to a cognitive problem. It can mean the dog has swallowed something they should not have, drugs, hemp, or CBD among them. And compulsive floor-licking carries a documented association with gastrointestinal disease. Make the call.
And sometimes a lick is just a thank-you
Do not overcorrect into paranoia. Licking is also communication in the ordinary, generous sense: a way of asking, of expressing gratitude, of saying that your attention is worth something.
A lick right after you have been petting a dog often means exactly what it looks like: either a request for more, or appreciation for what they already got. Licks can be plainly affectionate and ask for nothing at all, especially when they come with soft eye contact.
There is one honest caveat, and it is about you rather than the dog. Some dogs lick purely to get their owner’s attention, and if you reliably deliver attention whenever they do, you have taught them a very effective button. Before you conclude your dog has a problem, check whether your dog has simply trained you.
The bottom line
The mlem is not the message. In every case above, the thing carrying information is the licking itself (how much of it, where, and in what context), not the noise your pet makes while doing it.
“Mlem” is a funny bit of 2010s internet vocabulary, still gradually working its way into everyday speech. Enjoy it. Post the videos. Just do not let a meme talk you into reading a stress signal as a smile.
References
- Rugaas, T. On Talking Terms with Dogs: Calming Signals. Dogwise Publishing. (Foundational description of appeasement and displacement signals, including lip-licking.)
- Mariti, C. et al. “Perception of dogs’ stress by their owners.” Journal of Veterinary Behavior, 2012. https://www.sciencedirect.com/science/article/abs/pii/S1558787812000330
- American Veterinary Society of Animal Behavior. “Position Statement on Dog and Child Interactions.” https://avsab.org/resources/position-statements/
- Cornell Feline Health Center. “Psychogenic alopecia and compulsive grooming in cats.” https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center
- Bécuwe-Bonnet, V. et al. “Gastrointestinal disorders in dogs with excessive licking of surfaces.” Journal of Veterinary Behavior, 2012. https://www.sciencedirect.com/science/article/abs/pii/S1558787812000068
- Dictionary.com. “Mlem.” https://www.dictionary.com/e/slang/mlem/
