Source : Webster's Revised Unabridged Dictionary (1913)

Crown-saw \Crown"-saw`\ (-s?`), n. [From its supposed
   resemblance to a crown.] (Mech.)
   A saw in the form of a hollow cylinder, with teeth on the end
   or edge, and operated by a rotative motion.

   Note: The trephine was the first of the class of crownsaws.
         --Knight.