Green’s Dictionary of Slang

tit adj.1

[tit n.2 (1)]

pertaining to the female breast, usu. in context of pornography, e.g. in phrs. below.

[US]W. Kotzwinkle Midnight Examiner (1990) 100: How had this innocent child [...] come to be sitting on the floor of a tit publisher with a dart sticking through his nose?

In compounds

tit art (n.)

(US) pictures of attractive young women.

[UK]Guardian 2 June [Internet] In the new series, the boys get to play Mammary Man, in which five pairs of boobs are revealed by yanking off the pair of plastic breasts covering them up. Then, after the concealed girls all switch places, the ‘lucky’ bloke has to match the breasts to their owners. ‘It’s more tit-art than Brit-art!’ brays Denise, flashing her own.
tit book (n.)

a softcore pornographic magazine.

[UK]G.F. Newman You Flash Bastard 42: Claude Whatham was minding the shop, flicking through a pile of tit-books, part of a batch that had been taken.
tit mag (n.) (also tit magazine) [mag n.4 (1)]

a magazine which features scantily clad women. The pictures are interspersed with varying amounts of prose, reviews etc. but despite all other pretensions, they are in the end an aid to masturbation.

[US]M. Braly On the Yard (2002) 253: The wall behind him was solid with flicks clipped from different tit magazines.
[US]L. Heinemann Close Quarters (1987) 123: Drinking Thirty-three beer and thumbing through tit magazines.
[UK]M. Amis London Fields 381: Keep meself got up like a titmag.