The Collaborative International Dictionary of English v.0.48:

berkelium \ber*ke"li*um\ (b[~e]r*k[=e]"l[-e]*[u^]m), n. [from
   the city of Berkeley, California, location of the University
   of California campus where it was discovered.]
   a chemical element of the transuranic series. Chemical symbol
   Bk; atomic number 97; atomic weight 247. It is a radioactive
   element, with no stable isotopes; the longest-lived isotope
   is of mass number 247.07, decaying by alpha-emission with a
   half-life of 1,400 years. The isotope with atomic weight 249
   has a half-life of 314 days, and was isolated in weighable
   quantities.

   Syn: Bk.
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

berkelium
    n 1: a radioactive transuranic element; discovered by bombarding
         americium with helium [syn: berkelium, Bk, atomic
         number 97]

The Elements (07Nov00):

berkelium
Symbol: Bk
Atomic number: 97
Atomic weight: (247)
Radioactive metallic transuranic element. Belongs to actinoid series.
Eight known isotopes, the most common Bk-247, has a half-life of
1.4*10^3 years. First produced by Glenn T. Seaborg and associates in
1949
by bombarding americium-241 with alpha particles.