a) humping the air.
b) doing the nasty.

Can be used in context of other people/things, like "herping her derp" or "herping its' derp".
a) Guy: Yo, did you see Miley Cyrus herping her derp on that award ceremony last night?
Guy 2: Yeah, looked like she was having a seizure.

b) "Yeah, I was herping my derp last night with that cheap skank, I think I have AIDS now."
by r u srs June 25, 2010
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