What is the meaning of Transept?

The transversal part of a church, which crosses at right angles to the greatest length, and between the nave and choir. In the basilicas, this had often no projection at its two ends. In Gothic churches these project greatly, and should be called the arms of the transept. It is common, however, to speak of the arms themselves as the transepts.

transept

transept (transversal part of a church, which crosses at right angles to the greatest length, and between the nave and choir)

transept

Source: wiktionary.org