three-decker

Short definition from Wiktionary

Noun

1. 1
   Anything with three layers or levels.
2. 2
   Anything with three layers or levels: Alternative form of triple-decker (“type of sandwich”).
3. 3
   Anything with three layers or levels: Alternative form of triple-decker (“type of bus”).
4. 4
   Anything with three layers or levels: Alternative form of triple-decker (“type of apartment building”).
5. 5
   Anything with three layers or levels: Alternative form of triple-decker (“type of headline”).
6. 6
   Anything with three layers or levels: A sailing warship that had guns on each of three decks.
7. 7
   Anything with three layers or levels: An old-fashioned pulpit.