n. In anatomy, the lower one of three parts into which the small intestine is divisible, continuous with the jejunum and ending in the large intestine: more fully called intestinum ileum, from its many coils or convolutions.n. Hence, in general, the lower part, of indeterminate extent, of the small intestine; or, when there is no distinction between large and small intestine, a part of the intestine preceding the cæcum or the cæca.n. In entomology, a narrow part of the intestine of an insect, generally adjoining the ventriculus or stomach, and divided from the broader colon or second intestine by a constriction or valve.