Closed Mouth Smile (CMS) 

The act of smiling without showing one's teeth so the lips are stretched wide across the face while remaining closed. If done correctly, looks mischievous, but mostly creepy.

"Okay for this pic, don't smile, let's Closed Mouth Smile (CMS)."

Also a noun:

"That is one creepy looking CMS."

Closed Mouth Smile (CMS) by IFLEMV September 12, 2013

donkey mouth 

A bitch with huge fucking teeth and a voice that sounds like a pack a wild Native American horses dry humping

That bitch Evan is such a donkey mouth

donkey mouth by Imbeast55 October 13, 2013

Smash Mouth 

Once a band that were critically bashed for having catchy, if not downright cheesy, "tunes" like All Star and I'm a Believer, Smash Mouth are now hated for spreading the coronavirus across the godforsaken USA as a result of performing before a large packt crowd (a crowd without masks or social distancing) at the Sturgis Biker Rally back in August.

Somebody once told me
The virus was baloney
He ain't the sharpest tool in the shed
I was feeling kinda numb
With a burning in the lungs
And I said I don't think that it's COVID

Well the chills start coming
And they don't stop coming
Feelin' short of breath
Like I just went running
Didn't make sense to stay home
No fun
Instead went out
Infected everyone
So much to touch
So much to lick
So what's wrong with my little droplets
You'll never know if you don't test
Why do I feel pain in my chest?

Hey now
We're contagious
We're in Sturgis
No mask
Hey now
You're a biker
We're all sharing
One flask
This is worse than the flu
I'll be seeing you in the ICU

- Smash Mouth killing it in Sturgis with their hit song All Star. Fuck that COVID shit!

Smash Mouth by OK Dodo September 16, 2020

merc with a mouth

Nickname given to Marvel anti-hero Deadpool

Deadpool? That fucker is a merc with a mouth.

merc with a mouth by Maximus Cerillious September 15, 2016

Alright Mouth 

response to a mouthy comment made by any being in the genre of 'prick'...
randomly used by a variety of people in the bedfordshire and buckinghamshire counties...

pronounced: All-Right Moo-th

Annoying Chav: "you getting breezy blud? i'll knock you out!"
<your name here>: "Alright Mouth!"

Alright Mouth by lukey boy! March 6, 2008

Slaughter Mouth

A Slaughter Mouth can be a girl who loves to give blow jobs, or it can be another name for a blow job

Danny Mac: Wow, I was with that girl last night, she's quite the slaughter mouth. Gave me head alllll night long.

Rizzy Ryan: Yo I'm calling up nancy tonight for some slaughter mouth, she knows how to suck.

Slaughter Mouth by Danny519Mac May 31, 2009

Fountain Mouth 

The extreme salivation that usually sets in as a precursor to vomiting. Normally occurs during an extreme night of drinking, such as after a harsh shot or one beer bong too many.

I'd had like 13 beers, and I was doin fine. Then, Joe brought me the shot of Jack. As soon as I downed it, the Fountain Mouth kicked in, and I knew I was done. Next stop; Puke City.

Fountain Mouth by MikeyMxCx August 14, 2009