actinoid

Definitions of actinoid

1. noun

   any of a series of radioactive elements with atomic numbers 89 through 103
   synonyms: actinide, actinon

   type of:

   group, grouping

   any number of entities (members) considered as a unit
2. adjective

   having a radial form
   “starfish are actinoid--that is, they are radially symmetrical”

   synonyms:

   actinomorphic, actinomorphous

   capable of division into symmetrical halves by any longitudinal plane passing through the axis