Source : 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. & Zo["o]l.) Relating to a costa, or rib.

   {Costal cartilage}. See {Cartilage}, and Illust. of {Thorax}.

Source : WordNet®

costal
     adj : of or relating to or near a rib