/ Dictionary / Index T trunk piston: Meaning and Definition of Find definitions for: trunk' pis"ton Pronunciation: [key] — Mach. Mach. a piston with a long skirt to take the side thrust, as in an automobile engine. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. trunk line trunnel Related Content Daily Word Quiz: frugal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language