Green’s Dictionary of Slang

1. a search of a person’s clothes and body, either for security reasons or as a preliminary to picking their pocket; thus rub-down dippy n., a prison guard who searches new prisoners.

1933		J. Spenser Limey 259: From their cuff protectors I recognized them as ‘rub-down dippies’ – the men who search all arrivals for dope, liquor, guns and other contraband.
1937		E. Raymond Marsh 278: Given him a rub down? [...] Found anything?
1950		Goldin et al. DAUL 181/2: Rubdown. 1. A search of one’s person in which the hands are passed over the body and limbs outside the clothing.
1956		‘Raymond Thorp’ Viper 107: The Vice Squad were [...] picking you off the street for a quick rub-down - search.
1982		G. Newbold Big Huey 33: As we were about to get into the police ‘meat wagon’ which takes remand prisoners to court, the screws gave us a rub-down.
1996		J. Cameron It Was An Accident 21: Excuse me sir but I must just give you a quick rub down, you’ll understand for security reasons.

2. (orig. US black, also rub) a beating.

1896		‘Frederick Benton Williams’ (H.E. Hamblen) On Many Seas 398: If any of them are fractious, I’ll just give them a rub on their sore heads with my bone-softener.
1950		Goldin et al. DAUL 181/2: Rubdown. 2. (Rare) A beating administered in the course of an illegal third degree.