From Longman Dictionary of Contemporary Englishmainsailmain‧sail /ˈmeɪnsəl $ -seɪl/ noun [countable] TTWthe largest and most important sail on a ship
Examples from the Corpus
mainsail• The fully battened mainsail is loose-footed and stands a bold roach which has to brush past the backstay during a tack.• Whatever the urgency, setting more than the number three jib and the mainsail would have been stupid.• Yet somehow one hand remained on the wheel and the other clasped the mainsail winch.• Yesterday we had replaced yet another of the bamboo battens in the mainsail.• With just the mainsail out, the boat heeled hard off the wind on to a port reach.• I yelled at the crew to leave the work and lower the mainsail to just two panels.• The mainsail was still swinging back and forth, sweeping the cabin top, so it was lowered and tied down.• With mainsail set and at full throttle we steamed for home. 