Source : Webster's Revised Unabridged Dictionary (1913)

Acantha \A*can"tha\, n. [Gr. ? thorn, fr. ? point. See {Acute}.]
   1. (Bot.) A prickle.

   2. (Zo["o]l.) A spine or prickly fin.

   3. (Anat.) The vertebral column; the spinous process of a
      vertebra. --Dunglison.