| actinoid | (n) any of a series of radioactive elements with atomic numbers 89 through 103, Syn. actinon, actinide |
| actinoid | (adj) having a radial form, Example: starfish are actinoid--that is, they are radially symmetrical |
| Actinoid | a. [ Gr. &unr_;, &unr_;, ray + -oid. ] Having the form of rays; radiated, as an actinia. [ 1913 Webster ] |