ship of the line

a former sailing warship armed powerfully enough to serve in the line of battle, usually having cannons ranged along two or more decks; battleship.

Origin of ship of the line

First recorded in 1700–10

By three o'clock she had come near enough for Biddle to make out that she was a ship-of-the-line.

The Boys of 1812 and Other Naval Heroes |James Russell Soley
One ship-of-the-line was of course thought equivalent to two or three floating batteries, if opposed to them in an interval.

The Life of Nelson, Vol. II. (of 2) |A. T. (Alfred Thayer) Mahan
There fell an evil calm like this come two year ago when I was wrecked in a ship-of-the-line within sight of Havana.

Blackbeard: Buccaneer |Ralph D. Paine
Rather be a letter of marque, in fact, than a ship-of-the-line,—more credit to your Lordship's love of danger than discipline.

The Knight Of Gwynne, Vol. II (of II) |Charles James Lever

Upon every ship-of-the-line he had put five hundred picked men, who were daily exercised in working the guns.

Harper's New Monthly Magazine, Vol IV. No. XX. January, 1852. |Various

ship of the line

nautical (formerly) a warship large enough to fight in the first line of battle