Gaydar is a combination of the words "Gay" meaning "homosexually oriented" and "radar" (Pronounced Ray-dar)meaning a system that sends out radio waves and listens for their return to determine angle from radar source, and time lapse, to determine distance, and combines the two to determine postion and even movement. Gaydar acts more like a gay detector, and sound off when one is detected. Roll has one built in her battlesuit. It has activated for both Future X and Zero and Present X
It was orginally a gag in an episode of Futuramma in which they are trying to find Leela a boy friend. Bender continually calls men gay and cites he has a built in Gaydar.