Definition of americium in US English:

americium

noun

  • The chemical element of atomic number 95, a radioactive metal of the actinide series. Americium does not occur naturally and was first made by bombarding plutonium with neutrons.

    • ‘When americium was used as a target in this research, evidence for the formation of a new element was obtained.’
    • ‘Kept secret until after the war, they were respectively called americium and curium.’
    • ‘Internal contamination with plutonium, americium, or curium can occur through a variety of routes including ingestion, inhalation, or direct contact through wounds.’
    • ‘It was the first commercial manufacturer of plutonium and americium neutron sources for oil well, logging and other applications.’
    • ‘Trace levels of plutonium and americium from nuclear weapons tests in the 1960s can be found in most homes, as can radioactive isotopes of caesium from the Chernobyl accident in 1986.’

Origin

1940s: from America (where it was first made) + -ium.

Pronunciation