Actinide Definition

Any of a series of chemically similar, radioactive elements with atomic numbers ranging from 89 (actinium) through 103 (lawrencium).

Any of the elements in the series (actinide series) of radioactive, metallic chemical elements from element 89 (actinium) through element 103 (lawrencium): actinides resemble lanthanides in electronic structure.

Any of a series of chemically similar metallic elements with atomic numbers ranging from 89 (actinium) to 103 (lawrencium). All of these elements are radioactive, and two of the elements, uranium and plutonium, are used to generate nuclear energy.