adjective: (UK, military, nautical, historical) Of a Royal Navy ship of the line in the Napoleonic Era: having 50–60 guns across two gun decks, a complement of 320–420, and weighing approximately 1,000 tons burthen.
adjective: (idiomatic, uncommon) Terrible, awful; less than third-rate.
noun: (UK, military, nautical, historical) A fourth-rate ship of the line.