piston ring

split metal ring that fits into a groove on the rim of a piston to make a gas-tight seal 活塞环.

piquantly, pique, piquet, piracy, piranha, pirate, piratical, piratically, pirouette, Pisa, piscatorial, Piscean, Pisces, piss, pissed, pistachio, piste, pistil, pistol, piston, piston-engined, pit, pit pony, pit-a-pat, pit-a-pat (also pitter-patter), pit-head, pit-prop, pitch, pitch-and-toss, pitch-black, pitch-dark, pitch-pine, pitchblende, pitched, pitcher, pitchfork, piteous, piteously, piteousness, pitfall,