A "titwank" is when a woman masturbates a man with her breasts.
titwank.
titwank
It originated in medieval times, specifically from the small french village of Delivre, Bretagne (Brittany). In 1087, Katryn Tayt, the village's only milkmaid, engaged in what is now contemporarily known as a 'titwank'. As she was famed throughout the village for her flowing golden hair, milky white skin and heaving bosom, it become a rite of passage to receive a tiwank from Katryn. So, Tate became slang for 'Titwank' Raunchy, but true!
That is commonly referred to as "titty fucking" or "tit fucking". It is a sexual activity where a person thrusts their penis between someone else's breasts for stimulation.