transactinide element

transactinide element [trans-ak-tuh-nahyd, tranz-] Word Origin noun Chemistry, Physics.

1. 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.

See also transuranic element. Origin of transactinide element First recorded in 1965–70; trans- + actinide