Better known as fall season, and more particularly the month of October, when girls must decide how slutty they will look on Halloween.
Guy sees girl picking out Halloween "outfit."

Guy:"Damn, it's slut season already?"
Girl: "I heard that asshole!"
Guy: "IDGAF"
by andthesingoesto January 29, 2012
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girls that sleep with whoever is "in season", for example - girls who date around or sleep with whoever is on a sports team that is in season. just for attention.
Is that hoe sleeping with another sports team? What an in season slut.
by pinkcherriepie April 30, 2007
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