/ Dictionary / Index J jackshaft: Meaning and Definition of Find definitions for: jack•shaft Pronunciation: ( jak'shaft", -shäft"), [key] — n. Mach. Also calleda short shaft, connected by belting, gears, etc., that transmits motion from a motor or engine to a machine or machines being driven (distinguished from main shaft). a shaft on which an idle wheel or fairlead turns. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. jackscrew jacksmelt Related Content Daily Word Quiz: fabricate Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language