Source : Webster's Revised Unabridged Dictionary (1913)

Betulin \Bet"u*lin\, n. [L. betula birch tree.] (Chem.)
   A substance of a resinous nature, obtained from the outer
   bark of the common European birch ({Betula alba}), or from
   the tar prepared therefrom; -- called also {birch camphor}.
   --Watts.