Green’s Dictionary of Slang

1. a blunder.

1956		TV Guide 13–19 Oct. 4: Randolph Churchill...has told friends his embarrassment is assuaged by past goof-ups among English men of letters [OED].
1970		B. Seale Seize the Time 300: It was a goof-up.
1980		D. Burns Feeling Good 49: You exaggerate the importance of things (such as your goof-up or someone else’s achievement).
1993		N.Y. Times 26 Mar. A 29: Nobody out there knew what they were doing. It was one big goof-up [HDAS].

2. a person who blunders or messes up, causing trouble for themselves.

1957		M. Shulman Rally Round the Flag, Boys! (1959) 169: Still a captain? [...] You must be a bigger goof-up than I was!
1969		Linm & Pearl Masque of Honor 150: I can think of a few other gallant goof-ups who’ll get hurt if you kill Adam March’s brainchild [HDAS].
1980		D. Burns Feeling Good 136: You might label yourself a ‘total goof-up’.