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8.
What male virgins define as the orgasm they achieve after masturbating to pictures of dog porn on the internet.
"I had the best yiff ever last night, but now my laptop is stuck shut."
by HolyToiletWater July 16, 2012
 
9.
an addictive drug derived from coca or prepared synthetically, used as an illegal stimulant and sometimes medicinally as a local anesthetic. Otherwise known as cocaine.
Yo man, I gotta get off that yiff. The habit is costing me a fortune.
by pimpmaster1234 November 10, 2010
 
10.
(in the furry fandon)
to fornicate. (from the sound a fox in heat makes)
interjection (a greeting such as hello)
see also yiffy
verb "I yiffed her."
interjection "Yiff, Dark Fox."
by Colin Ritter August 06, 2003
 
11.
verb: to have netsex while pretending to be animals or furries (anthropomorphic animals), frequently practised in the furry fandom

noun: 1. a session of said netsex, 2. pornography featuring furries

adjective (yiffy): sexy or horny, in a furry context
"Hi, I'm an anthro white-tailed deer with a 12 inch cock, wanna yiff?"

"Doug Winger? He's that guy who draws nothing but yiff, isn't he?"

"U look yiffy, I want U be naughty on me"
by El Gatito Demoniaco December 21, 2002
 
12.
Internet intercourse between two or more furries.
We yiff with other "animals" online because we can't mate with our own species in real life.
by TG March 27, 2004
 
13.
To throw up or expel something from within.
I feel like i'm gonna yiff. Did you see that guy yiffing all over the place.
by Ty C May 21, 2006
 
14.
Term used by furfaggots to denote any form of sex, sexuality or anything of that sort. It usually involves an animal and is about the most fucked up thing on the planet.
Yiff in Hell furfags!
by CheeseAnonymous February 29, 2008