gaydar

noun [argot]
la suposada capacitat de discernir si una persona és homosexual (no sé si hi ha una expressió en catala o si és millor facilitar aquesta definició)

examples:

'I've never met a gay man who doesn't have at least a 3 out of 4 success rate with his 'gaydar'. I mean, he has to differentiate between straight and gay every time he sees an attractive man'.

'David Kopay, the former NFL running back who came out in the 1970s, says that on his one meeting with Troy (on a plane flight) his gaydar detected nothing'.