radioactive

from WordNet (r) 3.0 (2006)

radioactive
    adj 1: exhibiting or caused by radioactivity; "radioactive
           isotope"; "radioactive decay"; "radioactive fallout"
           [ant: {nonradioactive}]

from The Collaborative International Dictionary of English v.0.48

radioactive \ra`di*o*ac"tive\ (r[=a]`d[i^]*[-o]*[a^]k"t[i^]v),
   a. [Radio- + active.]
   1. (Physics) Capable of luminescence under the action of
      cathode rays, X rays, or any of the allied forms of
      radiation. [obsolete]
      [Webster 1913 Suppl.]

   2. (Physics) of, exhibiting, or caused by {radioactivity}.
      [PJC]