The act of putting a curtain between two males as they engage sexualy with a female situated in the middle. This lets the threesome occur without either male witness the others sweaty leering face and cumface. Reducing the result of a turn off. High fives may still occur around the side of the curtain.
when roughly two boys and a girl have a threesome, usually dressed in garments made from curtains and an eyepatch. the term originates from the victorian times, when slaves would often have to wear curtains and were very horny.
'man, when was the last time you were involved in a spot of curtaining???!!?! me and josh curtained millie last night sooo good!!! i love to curtain'