Green’s Dictionary of Slang

1. (US Und.) a fool.

1990		S. Morgan Homeboy 165: Jesus, what a lop.
1992		Bentley & Corbett Prison Sl. 36: Lop also Lop Head A stupid and ignorant individual.
1997		E. Little Another Day in Paradise 111: I [...] feel like I should change my name to Lenny the Lop.
2001		J. Stahl Plainclothes Naked (2002) 125: If you’d stop bein’ such a lop and let me finish . . .

2. (US) a contemptible person.

1977		E. Bunker Animal Factory 139: ‘Who is it?’ ‘Some lop fuckin’ with Ron.’.
2019		D. Winslow Border [ebook] ‘“A lop just checked in [...] Been going around talking about he’s in for armed robbery, but a wood in the office pulled his card—turns out he’s a chester’.

3. (US prison) in prison context of sense 1, an easily-victimized inmate.

1992

P. Earley Hot House 141: You can tell the rabbits, you know, the lops in here. They bring this guy in and he is doing time for some punk-ass white-collar rip-off, and right away I figure this guy’s got no heart. He’s a mark.

4. (US campus) an uncoordinated person.

1997–2000

Da Bomb 🌐 18: Lop: Uncoordinated.

5. (US prison) a second-rate prison officer.

2000		Other Side of the Wall: Prisoner’s Dict. July 🌐 Lop: A correctional officer who is a poor performer.
2006		Prison Slang Mommyblogger mydogharriet.blogspot.com 26 Sept. 🌐 If she treats you like a lop and tries to sleep you, Give her one warning, and calmly place her back in the bling.