Green’s Dictionary of Slang

1. to have sexual intercourse.

1937–84

Partridge DSUE (1984) 993/2: late C.17–early 19.

2. (also rub one off) to masturbate.

1972		B. Rodgers Queens’ Vernacular.
1993		J. Mowry Six Out Seven (1994) 97: Toby had lifted the snowy sheet to assure his mother that his new friends weren’t rubbing off.
2001		G. Pelecanos Right As Rain 85: The girls used their crotches, breasts and backsides to rub one off for the customers.
2012		G. Pelecanos (con. 1972) What It Was 79: Fanella’s trousers got right, and he went to the bathroom and rubbed one off in the privacy of a stall.