What's a "Gaydar"?

“I’ve got one who can see!” - They Live

Actually shown on Top Gear with Stephan Fry.

Is the wearer not looking to welcome the gay though, rather than banning it? Seems like a marketing nightmare.

As a teen I attended an all girls camp. I remember picking up that 11 and 12 year old girls in my activities were gay. Few years ago they popped up on Facebook…guess what? They’re all in realtionships with women.
I remember picking up that a friend of mine was gay. She wasn’t a Lilth Fair type at all…but I distinctly remember my gay dar BUZZING with her.
Two of my guy friends asked me how I knew…I don’t know…I just did.