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A disease that causes a person to be unable to not say derp (or herp ) for more than 24 hours, ranging in severity from one per day to one per sentence to "derpderpderpderpderpderpderpderpderpderpderpderpderpderpderpderpderpderpderpderpderp derpderpderpderpderpderpderpderpderpderpderpderpderp...".
Person 1: Did you hear? Bob suffers from severe derpitis. Derp!

Person 2: Are you sure you don't have it yourself?

Person 1: Derp.
by Rz2750 January 02, 2014