bwr(n = noun.artifact) boiling water reactor - a nuclear reactor that uses water as a coolant and moderator; the water boils in the reactor core and the steam produced can drive a steam turbine; Array
is a kind of water-cooled reactor

   a boiling water reactor; a type of nuclear reactor that uses water as a coolant and moderator; -- the steam produced can drive a steam turbine and produce electrical power. [WordNet 1.5]

bwr, abbr. boiling-water (nuclear) reactor.