Iliac \Il"i*ac\, a. [Cf. F. iliaque. See {Ileum}, and cf. {Jade} a stone.] 1. (Anat.) Pertaining to, or in the region of, the ilium, or dorsal bone of the pelvis; as, the iliac artery. [Written also {ileac}.] 2. See {Ileac}, 1. [R.] {Iliac crest}, the upper margin of the ilium. {Iliac passion}. See {Ileus}. {Iliac region}, a region of the abdomen, on either side of the hypogastric regions, and below the lumbar regions.