Noun
gaydar (countable and uncountable, plural gaydars)
(slang) The supposed ability to detect whether or not a person is gay by observing that person's appearance, mannerisms, etc. [from early 1980s]
Apparently, LGBT people are "those who self-identify as homosexuals," as if gaydar is totally not a thing. Source: Internet
Re: Mormon missionaries who set off one’s gaydar — My bi-dyke ex-girlfriend once said, “I sometimes see these clean-cut guys and I’m not sure if they’re gay, or just Christian.” Source: Internet