Used to describe a selfish person. Commonly used by navy machinists. If a person goes to a vending machine and doesn't ask anyone if they want anything.
"Hey shipmate, how's the soda?" Thank's for not asking me if I want anything. Fuckin' check valve."

"Hey look at that nub over there eating McDonald's. I'm not signing that check valves qual card."
by TorpMan, Submarines November 27, 2008
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A person who does not have the capability of seeing both sides of an arguement.
Following an arguement where the one person continues to not recognize that his/her point of view could not possibly be incorrect.... "Why cant you at a minimum see that the other side of the arguement could have some merit? You fucking check valve. You one way mother fucker!"
by JP7 March 12, 2009
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Refers to a careful inspection of the positioning/operation of a new/replacement one-way flow-stopper to make sure it's being installed in the correct "direction".
Zero was too stupid/unaware/forgetful to perform a "check valve" detail when hooking up the plumbing for the Camp Swampy mess hall, and so now there are geysers squirtiin' up all over da camp, but no water coming out in any of the kitchen-faucets --- just something more for Sarge to bellow about.
by QuacksO August 12, 2018
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A tiny little turd holding back What seems like 10 gallons of fart
I had to get to the shitter before that Mexican check valve went through my pants
by Fucko October 27, 2021
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