/ Dictionary / Index M mainsheet: Meaning and Definition of Find definitions for: main•sheet Pronunciation: (mān'shēt"), [key] — n. Naut. a sheet of a mainsail. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: mainsheet (Thesaurus) main shaft mainspring Related Content Daily Word Quiz: nonchalant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language