Source : Webster's Revised Unabridged Dictionary (1913)

Reniform \Ren"i*form\ (r?n"?-f?rm; 277), a. [L. renes kidneys +
   -form: cf. F. r['e]niforme.]
   Having the form or shape of a kidney; as, a reniform mineral;
   a reniform leaf.

Source : WordNet®

reniform
     adj : of a leaf or bean shape resembling the shape of kidney [syn:
            {kidney-shaped}]