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