Green’s Dictionary of Slang

1. (US Und./police) a trivial or minor offence, often used ironically, as in a charge of mopery and dopery.

1907		D. Runyon ‘The Defence of Strikerville’ in From First To Last (1954) 13: Come along [...] before the boogie man sloughs you in the skookum for mopery!
1922		N.Y. Tribune 1 Jan. 16/3: Dey just flung me outa de ahmy. Y’see Ah got co’t martial fo’ mopery or sumpin’.
1927		H. Yenne ‘Prison Lingo’ in AS II:6 281: Highway mopery — Hold up.
1934		(con. 1920s) J.T. Farrell Young Manhood in Studs Lonigan (1936) 294: We don’t want to get run in for mopery.
1947		N. Algren Neon Wilderness (1986) 23: How about mopery with intention to gawk?
1953		J. Thompson Criminal (1993) 75: I ought to sue ’em for mopery.
1961		G.L. Coon Meanwhile, Back at the Front (1962) 128: Indecent exposure, perhaps. Or mopery.
1975		E. Torres Carlito’s Way 16: Alma mater for many a mope majorin’ in thievery [...] and mopery.

2. (US prison, also mopry) contraband.

1918

H. Simon ‘Prison Dict.’ in AS VIII:3 (1933) 29/2: MOPRY. Contraband.

3. (US Und./police) stupidity or ineptitude.

1940		S.J. Perelman letter 23 May in Crowther Don’t Tread on Me (1987) 31: From that comes baldness and mopery.
1961		J. Heller Catch-22 (1962) 74: He was formally charged with [...] ‘indiscriminate behaviour, mopery, high treason, provoking, being a smart guy, listening to classical music, and so on’.
1972		K. Bonfiglioli Don’t Point That Thing at Me (1991) 40: I have had a long day, full of mopery and mayhem.

4. a second-rate figure.

1977

E. Torres Q&A 95: Hank is Larry Pesh’s boss. Larry is a mopery next to Hank.