One who constantly uses words(particularly the word(s) of the day) they found on this site and pretends/insists/swears/prays to god that you think that they were clever enough to make it up themselves. They know they aren't clever, but they don't want the rest of the world to think so.
An easy way to find one is to compare the word of the day list with the conversation/s you had with the suspected Urban Dictionary fag that day/s.
Mark: "Hey Jack, quick question
, do-*Jack interrupts*
Jack: "Mark, I've come to think you're an Urban Dictionary fag. I wrote down a few things you've said to me this past week. Let's take a look."
March 29 - "Mark: My electric razor broke, so I had to do an acoustic shave
March 28 - "Mark: Signing an email petition to stop rampant crime is slacktivism
. Want to really make your community safer? Get off your ass and start a neighborhood watch!"
March 27 - "Mark: I'm so twitterpated
about this movie!"
March 26 - "Mark: What do you mean foul!? We aren't playing Lawyer Ball
Jack: "I thought you went homo on the 27th, you didn't even think of your own sentence for the 28th and as for the 29th, you don't even shave. The verdict stands, you're an Urban Dictionary fag."
Mark: "You're just a Hobosexual
Jack: "December 4th."