Can be pertaining to a person or a thing.
*Friend trips and falls over own feet
You are so derpy sometimes
Derpy is best pony.
2. a title for someone who is often seen "herp-derping," whether in photographs or in real life
3. a good way to troll, or fool, others into admitting to embarrassing and most likely untrue diseases
John: "I don't know man, he looks like he's herp-derping."
Todd: "Herrrrrrrrp, I have derpies."
2. Sam: "You ever notice how Todd is always derping in pictures?"
Chris: "Yeah, it's weird, I wonder if he has derpies."
Todd: "Herrrrrrrp, I have derpies."
Sam: "You don't say...."
3. Troll: "Herp, I have derpies."
Victim: "Oh yeah? Well, derp, I have herpies."
Crowd: "Booh!" "Get off the stage!"