† semi-concaveObs. [semi- 7 a.] Applied to the half of a hollow cylinder bisected longitudinally. (See concave n. 1 b.) 1626Bacon Sylva §131 As the Enclosure, that is Round about and Entire, preserueth the Sound; So doth a Semi-Concaue.1734Builder's Dict.s.v. II. B 7, A Semi-Concave-Cylinder.