Green’s Dictionary of Slang

1. a blunder, an error, a confusion; also attrib.

1908		A.N. Lyons Arthur’s 82: I’m afraid he ’as made a bit of a muck-up of things.
1939		J. Campbell Babe is Wise 219: Makes a tie, religion. I mean when it’s the same. An’, my word can’t it make a muck up when it’s not!
1941		Sun (Sydney) 14 Oct. 7/4: You must have made a muck-up over the dates, mother.
1945		J. Henderson Gunner Inglorious (1974) 171: There seemed to be some trouble brewing up Gazala way. Benghazi had gone west four months ago and it looked like a muck-up again. We knew we’d be going into action soon.
1958		(con. WWII) F.I. Gwaltney Heaven and Hell 231: Grimes got sent to a muck-up company.
1959		W. Hall Long and the Short and the Tall Act I: So far on this outing it’s been the biggest muck-up in the history of the British army, and that’s saying a lot.
1960		R.M. Muir Word for Word 185: Proper bloody muck-up that’s going to be.
1976		R. Hall Glide Time 54: Why should I get in the cactus just because you make a muck-up?

2. (Aus.) a fight, a set-to.

1916

Forbes Times (NSW) 22 Aug. 4/4: The vessel wasn’t in the Jutland fight. This was a grievous disappointment to both officers and crew. They are just itching for a good old ‘muck-up’—something that will go the full twenty rounds and not one of these preliminary bouts.

3. of a person or situation, a mess.

1931		Wingham Chron. (NSW) 22 May 3/7: We wonder how they (the thinkers) fit in the awful ‘muck-up’ of to-day as part of progress.
1957		‘Weldon Hill’ Onionhead (1958) 266: ‘Why was that muck-up put ona gun in the first place?’.
1969		L. Hadow Full Cycle 139: There’s that pot-bellied muck-up that calls himself a winchman. Do I hate his guts! Muckin’ shame we can’t do the whole muckin’ issue on our pat.
1970		Times 15 Oct. 4: You cannot get away from the fact that Anzio was a bit of a muck-up.
1989		B. Reed ‘Messman on C.E.’s Altar’ in Passing Strange (2015) 21: Messman [...] had spotted this unholy muck-up [...] and was racing to the rescue.