tran·sept 
(trănsĕpt′)
(trănsĕpt′)n.
1. The transverse part of a cruciform church, crossing the nave at right angles.
2. Either of the two lateral arms of such a part.
[New Latin trānsēptum : Latin trāns-, trans- + Latin saeptum, partition; see SEPTUM.]
tran·septal (-sĕptəl) adj.