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.
Person 2: Are you sure you don't have it yourself?
Person 1: Derp.
by Rz2750 January 3, 2014
by Proshi November 14, 2011