Stands for Time to Dick Ride. Mostly used in online video games to talk about how bad your going to not only beat, but harass the other team.
Rooted from the phrase "Dick Rider". You harass nubs much as a Dick Rider would harass someone they love.
Gamer 1: Man these guys are nubs, time to dick ride!
Then you proceed to humiliate opponents.
Typical online conversation using AIM:
Gamer 1: This garbage clan wants to play us...lol
Gamer 2: TTDR!