The phrase "size up", usually used in arguments, essentially means to "stand up and fight"
"Yo, no long talkin' b. Either size up or nize up"

In other words...

"Hey man, I don't want to do this long talking business anymore. Either stand up to me and let's fight, or shut up."
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by suwayy March 26, 2017
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When two men are engaged in a heated argument and it is clear no resolution will be made, one male will say "size up", prompting both participants to expose their penises. The one with the larger penis wins the argument by default simply because his penis is larger. No exceptions.
Male 1: "Dude, you're a fucking dumbass, McDonalds is definitely better than Wendy's."

Male 2: "Um, are you fucking kidding me, Wendy's is 10 times better."

Male 1: "Size up"

Male 2: Alright, fine, McDonald's is better.
by VillanovaJC March 13, 2011
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when u measure each others cocks guys
''I'll measure urs if u measure mine'' That would be a size up.
by rw-lad August 13, 2008
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