Sometimes, slang used to refer to someone who is bisexual.

See also AC/DC.
"Is that guy heterosexual?" "Nah, he's AM/FM."
by dsm.textrevision September 5, 2004
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WHY DONT YOU JUST CHILLAX OR TURN ON THE RADIO! WOULD YOU LIKE AMMMM OR FFFMMMMMMM?!
“AM OR FM??? JUST CHOOSE ONE GODDANGIT”
by Mr.What Zit Tooya April 2, 2018
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