transactinide element

[ trans-ak-tuh-nahyd, tranz- ]
/ trænsˈæk təˌnaɪd, trænz- /

noun Chemistry, Physics.

any element having an atomic number higher than 103, the last of the actinide series. These superheavy, radioactive elements are extremely short-lived, and can only be created in the laboratory.

Origin of transactinide element

First recorded in 1965–70; trans- + actinide Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019