Green’s Dictionary of Slang

1. (US Und.) a member of the law-abiding public, by ext. a fool.

2002		Simon & Burns ‘The Target’ Wire ep. 1 [TV script] Two days ago no-one on this fuckin’ floor knew this mope’s name. Now he’s some kind of criminal mastermind.
2010		(con. 1973) C. Stella Johnny Porno 41: The mopes might figure out they’re fugazy.
2010		Codella and Bennett Alphaville (2011) 5: I love to shock the mopes.
2018		(con. 1963) L. Berney November Road 10: She shook off a mope who tried to make time with her.

2. (US) a (petty) criminal.

1990		D. Heilbroner Rough Justice 30: When we come walking down the block, the mopes all try to get rid of whatever they’re holding. It’s incredible. Maybe they think that if the stuff isn’t found on them they can’t be charged.
2005		R. Cea No Lights, No Sirens 19: [N]o mope with bad wiring is going to accelerate what is too short a gift anyhow.
2017		D. Winslow The Force [ebook] [Y]ou sympathize with the storeowner who just got robbed, but despise the mope who robbed him.