'Three-decker' definitions:

Definition of 'three-decker'

(from WordNet)
noun
Made with three slices of usually toasted bread [syn: club sandwich, three-decker, triple-decker]
noun
Any ship having three decks
noun
A warship carrying guns on three decks

Definition of 'Three-decker'

From: GCIDE
  • Three-decker \Three"-deck`er\, n. (Naut.) A vessel of war carrying guns on three decks. [1913 Webster]