n. The gallery of arches above the side-aisle vaulting in the nave of a church.
the GNU version of the Collaborative International Dictionary of English
n. 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.
The Century Dictionary and Cyclopedia
n. In medieval architecture, a gallery above the arches of the nave and choir, and often of the transepts, of a church, generally in the form of an arcade.
Word Usage
"The interior has a clean and fresh appearance owing to the recent restorations and is chiefly remarkable for the balustraded triforium which is continued round the whole church."