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 (._.)
