Green’s Dictionary of Slang

1. (also brunster) a homosexual, esp. a catamite or tramp’s young homosexual companion; by ext., a general derog.

1933		Ersine Und. and Prison Sl.
1949		Monteleone Criminal Sl. (rev. edn).
1952		J. Jones From Here to Eternity (1998) 3: All the brunser gets out of it is to play the Taps for funerals and sound Retreat for the shorttimer parades. [Ibid.] 318: He felt as if he had just witnessed the sodomitic seduction of a virgin brunser who had liked it.
1972		B. Rodgers Queens’ Vernacular 46: a homosexual teenager. Syn: brunster (dated, ’30s, hetero brunser = a homosexual+youngster). [Ibid.] 165: homosexual [...] brunser.
2004		J. Ellroy ‘Hot-Prowl Rape-O’ in Destination: Morgue! (2004) 307: I saw bisexual brunsers bruied and ripped from rubberhose techniques.

2. (US prison) the anus.

1960

(con. 1950-1960) R.A. Freeman Dict. Inmate Sl. (Walla Walla, WA) 18: Brunser – the opening at the lower end of the alimentary canal for excretion; anus .