1) Break off the masts of 2) Stop a galleon 
• (v. t.) To deprive of a mast of masts; to break and carry away the masts from; as, a storm dismasted the ship.
Dis·mast' transitive verb [ imperfect & past participle Dismasted ; present participle & verbal noun Dismasting .] [ Prefix dis- + mast : confer French démâter .] To deprive of a mast of masts; to break and carry ...
To lose, through breakage, part or all of the mast.
to deprive (a ship) of masts; break off the masts of.