Search Result for "actinide series":
Wordnet 3.0

NOUN (1)

1. (chemistry) a series of 15 radioactive elements with increasing atomic numbers from actinium to lawrencium; 



WordNet (r) 3.0 (2006):

actinide series
    n 1: (chemistry) a series of 15 radioactive elements with
         increasing atomic numbers from actinium to lawrencium