1. having gained an advantage in some way that betokens success, esp. over rivals.
2. leading an opponent by one point or one scoring unit: The home team was one up on the visitors.
3. one each; tied at a score of one: The score was one up in the ninth inning.
4. Print.with only one reproduction of a form per sheet or on a given sheet: We must print this job one up.
5. Journalism.using one more column of space than of type.
Pronunciation: (wun'up'), [key]
—v.t., -upped, -up•ping.
to get the better of; succeed in being a point, move, step, etc., ahead of (someone): They one-upped the competition.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.