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Cause : An action performed that is bound to go wrong because it hasnt been thought out right by the derp

Effect: Extremely awkward situation.
John meets his girlfriend Jen and hugs her.
John: Hi baby! I missed you!
Jen: Babe i missed you too!
John's best friend Sam who is also around hugs them both and wants to say "group hug" but says "Threesome".

Jen: you just killed it .Killed it.
John(Dissappointed): derptastic dude.

Sam: Derpa derpa derp.Hurr
by shyamieplaysguitar May 23, 2010
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a combination of derp and fantastic. can be used at anytime and is appropriate for almost any situation.
Jim: "I just totally hooked up with your cousin." Jacob: "That's derptastic, considering she has herpes and is addicted to cocaine and Doritos."
by eerisedsaysshutupkevin January 13, 2010
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