/ Dictionary / Index B back shaft: Meaning and Definition of Find definitions for: back' shaft" Pronunciation: [key] — Mach. Mach. a spindle carrying back gears. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. backset backshore Related Content Daily Word Quiz: paradox Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language