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slang An initialism of "Not/nothing much, you?" Used in text messages and online communications as a standard reply to the greeting "What's up?" and variants thereof. Often spelled in lowercase letters. A: "Yo dude. Wassup?" B: "NMU?" A: "nothin super bored lol" A: "Hey Chuck." B: "Hey. What's up?" A: " Eh, nmu"
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.