Mainmast

Part of Speech: Noun

Definition: The principle mast of a ship, typically the second mast in a sailing ship of three or more masts.

Source: Oxford Dictionaries

Found in ” My Boy Willie ” Line 35

Looking up the definition of mainmast helped me understand the passage. I had never seen the word before, so at first I looked at and said to myself: ” What in the world is this ?”