The act of sending ones housemate out to Tesco's to buy chocolate, muffins and wine in order to masturbate, naked in the middle of the living room, hoping that you can finish and redress yourself before they return home.
Margaret: What did you get up to last night?
Glynis: I had a dangerous wank whilst Brian popped to the shop for a pint of milk and some fishermans friends.
Margaret: Ooh, that sounds like fun.
Glynis: Yes, it was delightful.