Green’s Dictionary of Slang

sexual intercourse performed without a condom.

1963		in T.I. Rubin Sweet Daddy 110: Some of them use rubbers. But most guys want bare back.
1976		R. Price Blood Brothers 42: She takes her clothes off [...] and whips out a bag. [...] Awright, I prefer bareback, but it’s for my protection too.
1999		K. Sampson Powder 56: ‘Fifteen quid.’ ‘Oh. I thought you said ...’ ‘Aye. But bareback’s fifteen.’.
2009		J. Stahl Pain Killers 137: But they would do[...] Greek, Russian, bareback oral or facials.