Green’s Dictionary of Slang

1. usu. in passive, to defeat; thus mopped out, ruined.

1889		‘’Arry in Switzerland’ in Punch 5 Dec. in P. Marks (2006) 98: The Bullanger boom was a fizzle. They say he’s mopped out; I dunnow.
1910		Wodehouse Psmith in the City (1993) 143: This is pretty rocky. Three for sixty-three. We shall get mopped.
1915		Sun. Times (Perth) 5 Sept. 8: They acted ’s if their mob had all been mopped.
1993		K. Scott Monster (1994) 265: These Sixties niggas [...] mopped us at the Gladys Knight concert last night.
2001		Beanie Sigel ‘Get Down’ 🎵 in Source Aug. 186: You could get S.W.A.T. / You could get cops / They can get their shit mopped / Hit your block with semi and say gimme.
2018		CGM ‘No Porkies’ 🎵 YouTube gangsters, real life faggots / They get mopped and brushered (pussies).

2. (W.I./UK black) to beg, to ask for.

1956

S. Selvon Lonely Londoners 105: He would never mop a drink from anybody, it was he who always giving.

3. (US gay) to steal, esp. to shoplift.

1972

B. Rodgers Queens’ Vernacular.