Green’s Dictionary of Slang

1. badly broken or bent, damaged beyond repair.

1907		‘Yung-Kyum-Pyung’ in W. Jekyll Jam. Song and Story 12: The old-witch had a ’mash-up side.
1977		A. Clarke Prime Minister (1978) 101: The first lash really and truly had him mash-up, like a real hairpin.
1989		C. Hyatt When Me Was A Boy 70: We boys wi fine some ole half mash up train set wid some a the line missin.
1997		C. Newland Scholar 11: Not as ‘ruff’ as looking at mash up ham sandwich.
2001		(con. 1981) A. Wheatle East of Acre Lane 31: Follow me in your mash-up car.
2005		(con. c.1945) A. Wheatle Island Songs (2006) 47: We will give you [...] somewhere to rest ya mosh-up foot.
2005		(con. 1951) A. Wheatle Island Songs (2006) 107: Misser DaCosta’ s generator [...] inna de gulley. All mosh up.

2. thus in fig. use, e.g. used of someone exhausted or suffering from a hangover.

1986		R. Hewitt White Talk Black Talk 188: ‘’Ow d’you get on last night?’ ‘Oh I got mash-up bad’.
1999		(con. 1979–80) A. Wheatle Brixton Rock (2004) 196: I had to go to work [...] so if I went, I would have been all tired and mash up.

3. (UK black) under the influence of a drug.

2020

G. Krauze What They Was 63: Everyone gets too mashup and they start arguing [...] badding each other up .