tri·fo·ri·um 
(trī-fôrē-əm)
(trī-fôrē-əm)n. pl. tri·fo·ri·a (-fôrē-ə)
Architecture
Architecture
An arcaded gallery above the side-aisle arches and below the clerestory of a church.
[Medieval Latin, a gallery in Canterbury Cathedral (later taken to mean "with three openings").]