The Collaborative International Dictionary of English v.0.48:

mendelevium \men*de*le"vi*um\ (m[e^]n*d[e^]*l[=e]"v[=e]*[u^]/m),
   a. [From Dmitri Mendeleyev, discoverer of the periodic law.]
   (Chem.)
   an unstable radioactive element discovered in 1955 and
   produced artificially only in very small quantities; symbol
   Md (also Mv). It is a transuranic element with atomic number
   101. Isotopes 255, 256, 257, and 258 have been prepared.
   Md258, the longest-lived, has a half-life of two months.
   --HCP61
   [PJC]

WordNet (r) 3.0 (2006):

mendelevium
    n 1: a radioactive transuranic element synthesized by bombarding
         einsteinium with alpha particles (Md is the current symbol
         for mendelevium but Mv was formerly the symbol) [syn:
         mendelevium, Md, Mv, atomic number 101]

The Elements (07Nov00):

mendelevium
Symbol: Md
Atomic number: 101
Atomic weight: (256)
Radioactive metallic transuranic element. Belongs to the actinoid
series.
Only known isotope, Md-256 has a half-life of 1.3 hours. First
identified
by Glenn T. Seaborg, Albert Ghiorso and associates in 1955. Alternative
name unnilunium has been proposed. Named after the 'inventor' of the
periodic table, Dmitri Mendeleev.