When having sex with somebody from behind, the receiving partner reaches back with their
right arm and forcibly attempts to jam their fist
up the ass of the giving partner. Named after Thaal Sinestro, the arch nemesis of
the Green Lantern, the name is a reference to the fact Sinestro wears his power ring on his left hand so his right hand is free to penetrate people anally, as most supervillains often do with their free hands.
guy 1: I was
having sex with this girl
last night and I stuck it in her ass without telling her first.
guy 2: hahahaa what did she do?
guy 1: she wasn't happy so she gave me a right handed sinestro
to get even.
guy 2: Oh man that sucks!
guy 1: ...I kind of liked it (._.)