What is the meaning of Apse?

A semicircular projection from a building, especially the rounded east end of a church that contains the altar.

The bishop's seat or throne in ancient churches.

A reliquary, or case in which the relics of saints were kept.

Obsolete form of apsis (the nearest and furthest points to the centre of gravitational attraction for a body in orbit).

An aspen tree.

aspen tree (esp. Populus tremula)

abscess

Source: wiktionary.org