Green’s Dictionary of Slang

1. (gay) the penis.

1972		‘R. Cummings’ Bath Buddy 43: [T]he stud [...] casually brushing his boffer against my outstretched fingers [Simes:DLSS].
1974		‘L. Stewart’ Back Door Buddy 143: [R]eaching out as far as I could stretch, straining to get that big boffer in my hand [Simes:DLSS].

2. a masturbator [boff v. (3)].

1984

Partridge DSUE (8th edn) 108/1: since ca. 1930.

3. (US) one who has sexual intercourse [boff v. (2)].

1979		Frank Zappa ‘Broken Hearts Are for Assholes’ 🎵 The tale of a demented bread boffer.
1994		J. Wambaugh Finnegan’s Week 45: It takes a bimbo boffer like him to straighten out all the bitches in Washington.