n. In anatomy: In human anat, a superior and lateral part of the abdomen, beneath the lower ribs; one of the specific regions of the abdomen, situated on either side of the epigastrium, above the lumbar regions. See abdominal regions, under abdominal.n. Some abdominal region corresponding to the above, as the flank or side of the rump of a bird; an iliac region.n. plural In entomology, two lateral pieces at the base of the abdomen beneath, behind the metasternum and posterior coxæ: so called bv Kirby.