The Collaborative International Dictionary of English v.0.48:

Atomizer \At"om*i`zer\ ([a^]t"[u^]m*[imac]`z[~e]r), n.
   One who, or that which, atomizes; esp., an instrument for
   reducing a liquid to spray for disinfecting, cooling, or
   perfuming.
   [1913 Webster]

WordNet (r) 3.0 (2006):

atomizer
    n 1: a dispenser that turns a liquid (such as perfume) into a
         fine mist [syn: atomizer, atomiser, spray, sprayer,
         nebulizer, nebuliser]