A large square-rigged warship large enough to have a place in the line of battle, with up to 140 guns on at least two decks. A capital ship from the age of sail, superior to a frigate; usually, a seventy-four, or three-decker.
ship-of-the-line
How often have the words ship of the line and ship-of-the-line occurred in a corpus of books? (source: Google Ngram Viewer )