Final answer:
The transept is the part of a cruciform church that crosses the nave at a right angle, forming the church's cross-like shape.
Step-by-step explanation:
The major transverse part of a cruciform church that crosses the main axis at a right angle between the nave and the choir is known as the transept. The transept is crucial as it forms the arms of the cross shape in a church's architecture, giving the building a symbolic resemblance to a crucifix, thereby marking the Crucifixion. It is also functional in managing the flow of pilgrims, as seen in large pilgrimage churches such as those along the route to Santiago de Compostela.