A number or contact in one's phone book, specifically to call for casual sex. The abbreviation ISCF is short for In Case of Sexual Frustration. A close relative to the ICSF-numbers are the more common ICE-numbers (In Case of Emergency).
Person 1: What happened to the librarian-chick you were checking out by the bar.
Person 2: She had a boyfriend, dude.
1: Too bad, bro.
2: It's cool, I'll hook up with ICSF #5. Her apartment's five blocks down.
Person 2: She had a boyfriend, dude.
1: Too bad, bro.
2: It's cool, I'll hook up with ICSF #5. Her apartment's five blocks down.
by Mac & Missy July 27, 2010
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