Noun
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 dictionaryIn the case of Durham Cathedral, flying buttresses have been employed, but are hidden inside the triforium gallery. Source: Internet
The triforium (open arcade) above the door is unique in Scottish medieval architecture. Source: Internet
The triforium was omitted. Source: Internet
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. Source: Internet