a radioactive chemical element with a very short half-life: a transactinide produced by bombarding bismuth with high-energy nuclear particles: symbol, Mt; at. no., 109
See meitnerium in American Heritage Dictionary 4
(mīt-nûrˈē-əm)
noun Symbol Mt
An artificially produced radioactive element with atomic number 109 that has known isotopes with mass numbers ranging from 265 to 279. The isotope with the longest confirmed half-life (0.7 seconds) is Mt 268. Also called unnilennium. See Table at element.