A contraction of "if and when", used particularly when you are very certain of an outcome but still wish to provide an oppurtunity for being incorrect in your assumption.
Guy: Iffen you decide to come to my party, bring some strippers.
by Biguns April 21, 2006
Another much better way of saying "if". Note: Doesn't mean "if in"
Guy: Iffen you want some drugs come to my house
by krystal_kiss February 16, 2006
A much better, cooler variation of "if" often used in slang. **DOES NOT MEAN IF IN**
Guy:Iffen you want some drugs meet me in the park at 11:00.
by MonicaNiko February 16, 2006