Pronunciation: (thrē'dek'ur),[key] —n. 1. any ship having three decks, tiers, etc.
2. (formerly) one of a class of sailing warships that carried guns on three decks.
3. a sandwich made of three slices of bread interlaid with two layers of filling; club sandwich.
4. something having three layers, levels, or tiers. Also called triple-decker(for defs. 3, 4).