pistoning

Verb

piston (third-person singular simple present pistons, present participle pistoning, simple past and past participle pistoned)

1. (intransitive) To move up and down or in and out like a piston.
   • The Latino warrior fucked like a man possessed. His lean hips powered the pistoning rod in short, vicious jabs, so rapidly that the shit-streaked cock was a blur as it pounded Captain Randall's butthole, churning the screaming soldier's ass-juices, rectal blood, and smashed turds into a slimy froth.1991, Etienne, “In Enemy Hands”, in Drummer, number 151, page 32

See all 4 meanings of piston