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Similar to TGIF ( Thank God It's Friday ), meaning Oh No It's Monday
*alarm clock*

student: ughh...ONIM.
by spidiee August 23, 2009
An acronym standing for "Oh No, It's Monday".

Used to express the discontentment and dread one feels for Monday, the beginning of another tedious week.
Tito: "YES! let's get this weekend started!"
Todd: "You idiot, you've been passed out for 3 days."
Tito: "wait, what? O.N.I.M.!"
by ABDICKOX November 15, 2010