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"Nize It" is a phrase used to tell someone to be quiet or shut up, currently uknown to a majority of teachers, used in place of more vulgar or obscene phrase such as "Shut the F*uck up".
(people of authority nearby)
G: "yo B, you bring dat kush-"
B: "Nize it G, we'll talk later."

Teacher(in the middle of lecture): "so the electrons are-"

G: " just Nize it"
Teacher: " What does that mean mr. Green?"
S: "Um, it means i like your style."
Teacher: "You crazy kids and your slang these days."
by Bramptonian Rhapsody June 05, 2011
another way to tell someone to be quiet, or to 'shut the fuck up'.
X: "yo, that bitch has a fatttt assss."
Y: "nize it, she is like a pancake. no lie."
by dome squad March 18, 2014