Slang way to tell someone to shut up, commonly used to replace vulgar, or obscene phrase such as Shut The F**K Up. Unknown by Teachers.
Arturo: Yo, Mark you're so ugly!
Mark: Nize Your Beak! Have you looked in the mirror?
Arturo: Yeah, what about you?
Mark: I said Nize Your Beak!
by FAM27 November 30, 2017
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Short for "Recognize your beak". This meaning you better watch what you say fam

Straight from T-dot
Scrub: "Yo dawg ur a batty boy!"

Fam: "Nize your beak!"
by Dick_puncher69 May 21, 2017
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