A "titwank" is when a woman masturbates a man with her breasts.
titwank.
titwank
A 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!