technetium
noun
tech·ne·tium tek-ˈnē-sh(ē-)əm 
: a radioactive metallic element obtained especially from nuclear fuel as a product of uranium fission and used as a diagnostic radiopharmaceutical see Chemical Elements Table
Example Sentences
Recent Examples on the Web Still, Lawrence’s cyclotrons allowed element hunters to take trillions of shots, and by 1937 one of his devices had created technetium (element No. 
Neima Jahromi, The New Yorker, 27 Dec. 2019 Like all elements first born in cyclotrons, technetium was radioactive. Neima Jahromi, The New Yorker, 27 Dec. 2019
Neima Jahromi, The New Yorker, 27 Dec. 2019 Like all elements first born in cyclotrons, technetium was radioactive. Neima Jahromi, The New Yorker, 27 Dec. 2019 Word History
Etymology
Greek technētós "artificial" (verbal adjective of technáomai, technâsthai "to make with skill, contrive cunningly," verbal derivative of téchnē "art, skill, proficiency in an art or craft, (in plural) wiles, cunning") + -ium; so named because it was the first element to be synthesized artificially — more at technical entry 1
Note: The element was named by the Italian mineralogist Carlo Perrier (1886-1948) and the Italian-American physicist Emilio Segrè (1905-89), who had earlier isolated isotopes; see C. Perrier and E. Segrè, "Technetium: the element of atomic number 43," Nature, vol. 159, no. 4027, January 4, 1947, p. 24.
First Known Use
circa 1946, in the meaning defined above
Medical Definition
technetium
noun
tech·ne·tium tek-ˈnē-sh(ē-)əm
: a metallic element that is obtained by bombarding molybdenum with deuterons or neutrons and in the fission of uranium and that is used in medicine in the preparation of radiopharmaceuticals —symbol Tc see pertechnetate Chemical Elements Table