Definitions for mainsheetˈmeɪnˌʃit
Random House Webster's College Dictionary
a sheet of a mainsail.
Origin of mainsheet:
sheet, tack, mainsheet, weather sheet, shroud(noun)
(nautical) a line (rope or chain) that regulates the angle at which a sail is set in relation to the wind
The rope connected to and controlling the mainsail.
one of the ropes by which the mainsail is hauled aft and trimmed