the series of radioactive elements that starts with actinium and ends with lawrencium.
Origin of actinide series
First recorded in 1940–45
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for actinide series
a series of 15 radioactive elements with increasing atomic numbers from actinium to lawrencium
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012