1. The act of licking your fingers in a suggestive (often sexual) way.
2. The act of dipping your fingers in a girl's vagina, and making raspberries while pulling in/out.
Dude- why the hell did you dippyderp in front of me? You're seriously questioning my sexuality....
Second def. example:
Dude, I so dippyderped Jess' pussy last night, though she called me an immature ass later. Oh- here! I recorded it. Dippity dip derp dop doop derp dippity jim jam.