calotte

noun

1. a skullcap worn by Roman Catholic priests

2. (archaic) The vertical central area of the crown of a bird's head.

3. (architecture) A round cavity or depression, in the form of a cup or cap, lathed and plastered; used to diminish the rise or elevation of a moderate chapel, alcove, etc. which would otherwise be too high for other pieces of the apartment.

4. (anatomy) The upper (superior) or lower (inferior) half of the globe of the eye.