Source : Webster's Revised Unabridged Dictionary (1913)

Creatin \Cre"a*tin\ (kr?"?-t?n), n. [Gr. ??? flesh.] (Physiol.
   Chem.)
   A white, crystalline, nitrogenous substance found abundantly
   in muscle tissue. [Written also {kreatine}.]

Source : WordNet®

creatin
     n : an amino acid that does not occur in proteins but is found
         in the muscle tissue of vertebrates both in the free form
         and as phosphocreatine; supplies energy for muscle
         contraction [syn: {creatine}]