abbreviation for "U-R-Funny". Alternate response to a funny statement (usually response to an electronic message) instead of the typical "LOL" .
Boy: Hey, guess what... I threw your ex-bf in the mud.
Girl: URF! Thnx! But we're back together!
Girl Walrus: Hey, who wants a beach ball?
Boy Walrus: URF! URF! URF!