Webster’s Revised Unabridged Dictionary · 1913 Costal Cos′tal (k?s′tal), a. [Cf. F. costal. See Costa.] 1. (Anat.) Pertaining to the ribs or the sides of the body; as, costal nerves. 2. (Bot. & Zoöl.) Relating to a costa, or rib. Costal cartilage. See Cartilage, and Illust. of Thorax. ‹ Costage Costal-nerved ›