Green’s Dictionary of Slang

tit adj.1

[tit n.2 (1)]

[1950s+] pertaining to the female breast, usu. in context of pornography, e.g. in phrs. below.

In compounds

tit art (n.)

[1950s+] (US) pictures of attractive young women.

tit book (n.)

[1970s] a softcore pornographic magazine.

tit mag (n.) (also tit magazine) [mag n.4 (1)]

[1960s+] 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.