Definition of "fermium" []

• A synthetic transuranic metallic element (atomic number 100) having 10 isotopes with mass numbers ranging from 248 to 257 and corresponding half-lives ranging from 0.6 minutes to approximately 100 days. See Table at element. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The first glimpse at 112 lasted for only a third of a millisecond, until it decayed first into element 110 (darmstaditium) and then into four different short-lived elements until researchers lost its trail at element 110 (fermium)."