Buttcape
Definition
"Buttcape" is a frequently-used term which refers to the flowing cape-like garments most Widows and Fortunatas wear, which extends from the waist to the ankles. It bears similarities to the cape design "Fortune", but obviously, worn from the waist. All of the current Widow NPCs who offer missions, such as Ghost Widow and Seer Marino, wear the "buttcape".
In out-of-game usage, it would be commonly called a coattail.
Much to the dissatisfaction of a large majority of the players, Arachnos Widow, the villain epic archetype, did not come with the option of having the "buttcape" as a costume choice.
Tongue-in-cheek complaints on the official forums about the exclusion of "buttcapes" have led to developers such as JLove and Back Alley Brawler joking about writing letters to the people in charge (i.e. themselves) with letters starting with "Dear jerks".