triple-decker

tri·ple–deck·er

noun, often attributive \ˌtri-pəl-ˈde-kər\

: something that has three levels or layers

Full Definition of TRIPLE-DECKER

:  something having three basic components or levels: as

a :  trilogy

b :  a sandwich consisting of three pieces of bread and two layers of filling

c :  a 3-story dwelling with an apartment on each floor

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First Known Use of TRIPLE-DECKER

1938