unf 

Universal Noise of Fucking. See above definition for onomatopoeic use as a sound itself.

unf by Video Warrior Laserion December 14, 2002

unf 

A term used to express sexual desire

Unf that guy is so HOT!

unf by Hella cool April 18, 2014

Unf 

Common word used on Tumblr when seeing a hot person.

hot.
UNF

Unf by hookerific August 23, 2011

unf 

Universal noise of fucking. Also used to describe someone attractive.

Damn, Alex Gaskarth is so unf.

unf by wtfamisupposedtoputhere? October 22, 2011

UNF 

sexual. Accronym for "Universersal Noise for Fucking"
particularly heard during intercouse when the female moans but bites her lip to silence herself. "unf" heard as "uuuuhhhfff" or "ooooouuuhhhnnnnnfff"

"all that bitch could say was unf"

UNF by -GT April 10, 2006

uNf 

The noise that the Doom guy made when you tried to 'open' a wall like it was a door. uNF uNF

uNF uNF uNF uNF oh shit, this is a wall, not the door leading to the floating eyeball.

uNf by dC//jANGEY June 11, 2003

Unf 

Same as, "blown". Origin: The sound a guy makes when he cums.

"Unf, I have that paper due in two hours and I haven't even started."

Unf by Awesomenesssss213 March 5, 2012