a hypothetical celestial object consisting of a body of gas that gives off a small amount of radiation but lacks sufficient mass to initiate the nuclear fusion that characterizes true stars
See brown dwarf in American Heritage Dictionary 4
noun
A celestial body with insufficient mass to sustain the nuclear fusion that produces radiant energy in normal stars, believed to have formed with enough mass to start nuclear fusion in its core, but without enough for the fusion to become self-sustaining.