The Collaborative International Dictionary of English v.0.48:

Radium \Ra`di*um\ (r[=a]"d[i^]*[u^]m), n. [NL., fr. L. radius
   ray.] (Chem.)
   An intensely radioactive metallic element found (combined) in
   minute quantities in pitchblende, and various other uranium
   minerals. Symbol, Ra; atomic weight, 226.4. Radium was
   discovered by M. and Mme. Curie, of Paris, who in 1902
   separated compounds of it by a tedious process from
   pitchblende. Its compounds color flames carmine and give a
   characteristic spectrum. It is divalent, resembling barium
   chemically. The main isotope of radium found in pitchblende,
   radium-226, has a half-life of 1620 years, decaying first by
   alpha emission to radon.

   Note: Radium preparations are remarkable for maintaining
         themselves at a higher temperature than their
         surroundings, and for their radiations, which are of
         three kinds: alpha rays, beta rays, and gamma rays (see
         these terms). The beta and gamma rays seen in radium
         preparations are in fact due to disintegration of decay
         products of radium rather than the radium itself. By
         reason of these rays they ionize gases, affect
         photographic plates, cause sores on the skin, and
         produce many other striking effects. Their degree of
         activity depends on the proportion of radium present,
         but not on its state of chemical combination or on
         external conditions. The radioactivity of radium is
         therefore an atomic property, and is due to an inherent
         instability of the atomic nucleus which causes its
         decay in a process whose rate is first order. The
         disintegration of the radium nucleus is only the first
         in a series of nuclear disintegrations leading to
         production of a series of elements and isotopes. The
         chain has at least seven stages; the successive main
         products have been studied and are radon, a gaseous
         radioactive element belonging chemically to the inert
         noble gas series (originally called radium emanation or
         exradio, radium A, radium B, radium C, etc. The
         successive products are unstable isotopes of several
         different elements, each with an atomic weight a little
         lower than its predecessor. Lead is the stable end
         product. At the same time, the light gas helium is
         formed, being generated when the expelled alpha
         particles (positively charged helium nuclei) acquire
         electrons. Radium, in turn, is formed in the
         pitchblende ore by a slow disintegration of uranium.
         Natural radium and also an isotope (radium-228, also
         called mesothorium I) formed by the decay of thorium,
         were at one time used to make a luminous paint for
         watch dials, until the danger of the radioactivity
         became fully appreciated, and use of such material in
         watches was discontinued. See also mesothorium.
         [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

radium
    n 1: an intensely radioactive metallic element that occurs in
         minute amounts in uranium ores [syn: radium, Ra,
         atomic number 88]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "radium":
   acid, actual cautery, americium, astatine, atomic cocktail,
   berkelium, brand, brand iron, branding iron, caustic, cauter,
   cauterant, cauterizer, cautery, cobalt, corrosive, curium,
   einsteinium, electrocautery, escharotic, fermium, francium,
   hahnium, hot iron, lunar caustic, mendelevium, mordant, moxa,
   neptunium, plutonium, polonium, potential cautery, promethium,
   protactinium, radiocalcium, radiocarbon, radioelement, radioiodine,
   radioisotope, radiosodium, radon, tagged element, technetium,
   tracer, uranium



The Elements (07Nov00):

radium
Symbol: Ra
Atomic number: 88
Atomic weight: (226)
Radioactive metallic transuranic element, belongs to group 2 of the
periodic table. Most stable isotope, Ra-226 has a half-life of 1602
years,
which decays into radon. Isolated from pitchblende in 1898 Marie and
Pierre Curie.


The Devil's Dictionary (1881-1906):

RADIUM, n.  A mineral that gives off heat and stimulates the organ
that a scientist is a fool with.


U.S. Gazetteer Places (2000):

Radium, KS -- U.S. city in Kansas
   Population (2000):    40
   Housing Units (2000): 19
   Land area (2000):     0.041442 sq. miles (0.107335 sq. km)
   Water area (2000):    0.000000 sq. miles (0.000000 sq. km)
   Total area (2000):    0.041442 sq. miles (0.107335 sq. km)
   FIPS code:            58300
   Located within:       Kansas (KS), FIPS 20
   Location:             38.173698 N, 98.894222 W
   ZIP Codes (1990):     67550
   Note: some ZIP codes may be omitted esp. for suburbs.
   Headwords:
    Radium, KS
    Radium