n. A semicircular hollow or opening among trees or hills. Wordsworth. [ 1913 Webster ]
n. 1. (a) The half of a circle; the part of a circle bounded by its diameter and half of its circumference. (b) A semicircumference. [ 1913 Webster ]
2. A body in the form of half of a circle, or half of a circumference. [ 1913 Webster ]
3. An instrument for measuring angles. [ 1913 Webster ]
a. Semicircular. Shak. [ 1913 Webster ]