n. pl. carinæ (-nē). [L., the keel of a boat: see careen.] A keel.n. An intermediate piece, between the tergum and the scutum, of the multivalve carapace of a cirriped, as a barnacle or an acorn-shell. See cuts under Balanus and Lepas.n. [capitalized] In astronomy, one of the four parts into which the constellation Argo is divided. See Argo.n. One of the vertical cross-bars on the septa of a coral.n. In entomology, any keel-like elevation of the body-wall of an insect, as the pronotal carina of many grasshoppers.