WordNet (r) 3.0 (2006):

nobelium
    n 1: a radioactive transuranic element synthesized by bombarding
         curium with carbon ions; 7 isotopes are known [syn:
         nobelium, No, atomic number 102]

The Elements (07Nov00):

nobelium
Symbol: No
Atomic number: 102
Atomic weight: (254)
Radioactive metallic transuranic element, belongs to the actinoids.
Seven
known isotopes exist, the most stable being No-254 with a half-life of
255
seconds. First identified with certainty by Albert Ghiorso and Glenn T.
Seaborg in 1966. Unnilbium has been proposed as an alternative name.