A triple-decker is a term used to describe something that has three layers. In the context of a crossword, the term 'triple-decker' can refer to two solutions: 'CLUB' (4 letters) and 'clubsandwich' (12 letters). A CLUB is a type of card game typically played with four players and a standard deck of 52 cards. A CLUB sandwich is a type of sandwich made with three slices of bread, usually filled with lettuce, tomato, bacon, and mayonnaise.