Source : Webster's Revised Unabridged Dictionary (1913)

Urobilin \U`ro*bi"lin\, n. [1st uro- + bile + -in.] (Physiol.
   Chem.)
   A yellow pigment identical with hydrobilirubin, abundant in
   the highly colored urine of fever, and also present in normal
   urine. See {Urochrome}.

Source : WordNet®

urobilin
     n : brown bile pigment formed from urobilinogens and found in
         feces and in small amounts in urine