/ Dictionary / Index S spiral gear: Meaning and Definition of Find definitions for: spi'ral gear' Pronunciation: [key] a type of helical gear used for transmitting power between shafts that are at an angle to each other. See Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. spiral galaxy spiral nebula Related Content Daily Word Quiz: procrastinate Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language