Source : Webster's Revised Unabridged Dictionary (1913)

Actinoid \Ac"tin*oid\, a. [Gr. ?, ?, ray + -oid.]
   Having the form of rays; radiated, as an actinia.

Source : WordNet®

actinoid
     adj : having a radial form; "starfish are actinoid--that is, they
           are radially symmetrical"
     n : any of a series of radioactive elements with atomic numbers
         89 through 103 [syn: {actinide}, {actinon}]