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Acronym for:
I'm So Sexually Frustrated.
X: "I SWEAR dude, she was grinding against my package nonstop at the party!"

O: "Wow, sounds like a real ISSF moment.."
by wchistia July 04, 2011
"Insert Sideways Smiley Face"
because emoticon is a stupid name, and lol is usually used to mean "smile." plus, using a cryptic acronym to stand for an over-used geek phenomenon has a beautiful circularity.
"i wanted to get my definition into UrbanDictionary.com, ISSF."
by meme March 22, 2005