Herp Derp Share definition Flag An expression used when a person, or yourself, has done somthing extremely stupid and dopey Person 1: Dude, I just hit my head on the door. Person 2: HERP DERP. Herp Derp by Kommandant November 25, 2009 Words you can keep railfan mug chonk mug chud mug based mug 67 mug slime mug mogging mug chopped mug thot mug glazing mug huzz mug yams mug larp mug unc mug cracked mug simp mug baddie mug bop mug lolcow mug