semicircular

Other forms: semicircularly

Something that is semicircular is shaped like a circle — a round, closed shape — but cut in half. A half-moon is one semicircular shape visible twice each month, as half the side of the moon facing Earth is illuminated.

The prefix semi- is borrowed from Latin, and it means "half." So a semicircle is half a circle: If you cut a circle on a straight line going from end to end right through its center, you'll end up with two semicircles. The adjective semicircular describes things that have the general shape of a semicircle, such as the entrance to a tunnel, a protractor for measuring angles, or half a round pizza pie!