I.a cutting into, incision, incisure (post-Aug.).
II. In partic.
A. A natural incision, indentation; as in the palm of the hand, the bodies of insects, in leaves, etc., Plin. 11, 52, 114, § 274; 11, 1, 1, § 1; 15, 11, 11, § 37; 26, 8, 29, § 46.—
B. In painting, a division between the light and shade, Plin. 33, 13, 57, § 163.