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1. Someone who is really dumb
2. A person who doesn't/can't breathe through their nose
by A-Claire February 20, 2017
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2
1. literally, someone who lacks enough intelligence that they never learned to breathe through their nose.

2. a really dumb person.
In his latest work, the director has forsaken the indie audience and made something for the mouthbreathers.
by hedgerow September 03, 2003
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3
A stupid person who breathes through their mouth, like P Diddy.
P Diddy is a mouth breather
by ===0) December 29, 2004
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4
1. Someone who is incapable of breathing through their nose

2. Someone stupid who is unaware that their mouth is gaping open, often taking in gallons of air and spewing their own dry, bacteria rotten maw into your clean air in your vicinity.
Never let a mouth-breather speak to you very close, or you might regret it.
by Randall Wynn April 06, 2008
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5
A person who breathes through their mouth, thus having their mouth hang open. Their mouth can be anywhere from barely open, to gaping, and usually the more open it is, the more idiotic, and unintelligent they look. Mouth Breathers may or may not be intelligent, however, due to the fact that they don't realize their mouth is gaping, they just look like a moron, who may drool at any moment, but is deffinately sucking in as much air as possible.

Mouth breathers tend to be people who are bored, zoning out, very focused on something, someone with huge lips, or someone who isn't smart enough to realize their mouth is hanging open, catching flys. All tend to appear as the latter.

People who are sick and can't actually breathe through their noses do not count.
Katie: "I was sitting in class, and I looked over at Fred, who was staring dead eyed at the board with his mouth hanging open, like an idiot"

Rachel: "Ew, what a Mouth Breather"
by JelloLove September 15, 2010
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6
General term for a fucking idiot.

Usually seen with a blank stare on their face, mouth slightly agape, and possibly a little bit of drool coming out.
The new temp workers we got are a bunch of mouth breathers.
by Must Love Chest Hair December 19, 2017
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7
A person of inferior intellect that lacks the faculties to recognize he is breathing heavily through his drooping open mouth; one who watches Fox News and Nascar with religious zeal.
Donnie shops at Evil-Mart like all the other mouth breathers.
by Joe Flood September 04, 2007
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