From Longman Dictionary of Contemporary Englishmainmastmain‧mast /ˈmeɪnmɑːst, -məst $ -mæst, -məst/ noun [countable] TTWthe largest or most important of the masts on a ship
Examples from the Corpus
mainmast• As they surged against the mainmast they broke and splashed in foam and spray which flicked into the cabins.• Jess turned sharply and saw a tall Negro coming from behind the mainmast.• With the sun shining on them, the insects became more active, and climbed the mainmast.• The worst situation was amidships, by the base of the mainmast.• It would be better to replace the mainmast as well as the foremast while we had the chance.• During that crucial ten minutes I feared the wind pressure would rip the mainmast out.• One of the main shrouds, the ropes which supported the mainmast, was about to break. 