Green’s Dictionary of Slang

bishop n.2

[SE bishop ]

1. [early 18C–19C] a mixture of wine and water, topped off by a roasted orange, supposedly an episcopal favourite.

2. the size/rotundity of the stereotypically well-fed clergyman.

(a) [late 18C–early 19C] a large condom.

(b) [mid-19C] (US) ? a form of woman’s makeup container.

(c) [late 19C] a bustle.

(d) [late 19C–1900s] a chamberpot.

(e) [late 19C+] (US black/campus) the penis.

(f) [1940s] (UK Und.) a folding jemmy.

3. [mid–late 19C] a broken signpost [mild anti-clericalism: it neither points the way nor travels it].

4. [1950s–70s] a private detective [he ‘searches out sin’].

In phrases

bang one’s bishop (v.) (also bash one’s/the bishop, beat the bishop, bop..., capture..., choke..., flip..., flog..., polish...) [ety. unknown, although DSUE suggests a resemblance of the penis to a bishop’s mitre or to the bishop in a trad. designed ‘Staunton’ chess set; however, simple assonance is equally likely/bash v. (1)/bop v. (1)]

[late 19C+] to masturbate; thus bishop-bashing n., masturbation.