triforium
Noun
Meaning
The gallery or open space between the vaulting and the roof of the aisles of a church, often forming a rich arcade in the interior of the church, above the nave arches and below the clearstory windows.
Source: Webster's dictionarySynonyms
Examples
In the case of Durham Cathedral, flying buttresses have been employed, but are hidden inside the triforium gallery.
The triforium (open arcade) above the door is unique in Scottish medieval architecture.
The triforium was omitted.
This can be seen from the many examples of features that would be unlikely in a contemporary church, including the placing of a round arched triforium above a pointed colonnade in the Berlin work.