Green’s Dictionary of Slang

1. a blunder, a botch.

1902		C.J.C. Hyne Mr Horrocks, Purser 111: At a rough guess, I should say he feels this mess-up more than any of us .
1934		J. Franklyn This Gutter Life 28: I’m rather a mess-up, you know!
1946		G. Gibson Enemy Coast Ahead (1955) 37: What a complete mess up!
1950		A. Buckeridge Jennings Goes To School 103: And now what a ghastly mess-up it all was!
1960		L. Davidson Night of Wenceslas 62: A terrifying thought had struck me [...] that there might be some mess-up on the actual day.
1988		W.D. Myers Fallen Angels 5: The only reason I was going [to Vietnam] anyway was because of a paperwork mess up.

2. (Aus.) a fight.

1912

Bulletin (Sydney) 5 Dec. 13/4: There has been a little mess-up in Melbourne, and a discolored brother has got his face broken. The mêlée was pretty brisk while it lasted, and might easily have been worse.

3. an inadequate or incompetent person, a person with problems.

1924		S. Scott Human Side of Crook and Convict Life 21: Leave the chap alone. He’s a damned mess-up as it is.
1970		N.J. Johnson ‘About This Thing Called Ghetto Education’ in Szwed Black America 252: [I]f a student, a genuine mess-up, chooses at a given point in time to grow and learn [...] there is an opportunity for him to do so with no preconditions.