Wiktionary
copropraxia
n. An involuntary impulse to make obscene gestures
Wikipedia
Copropraxia
Copropraxia is a tic consisting of involuntarily performing obscene or forbidden gestures, or inappropriate touching. Copropraxia comes from the Greek κόπρος meaning " feces" and πράξις meaning "action". Copropraxia is a rare characteristic of Tourette syndrome.
Related terms are coprolalia, referring to involuntary usage of profane words, and coprographia, making vulgar writings or drawings.