The Collaborative International Dictionary of English v.0.48:

Nephelometer \Neph`e*lom"e*ter\
   (n[e^]f`[-e]*l[o^]m"[-e]*t[~e]r), n. [Gr. nefe`lh a cloud +
   -meter.]
   1. An instrument for measuring or registering the amount of
      cloudiness.
      [1913 Webster]

   2. (Chem., Microbiol.) An instrument which measures the
      degree to which liquid suspensions scatter light, and by
      inference, the concentration of scattering particles in
      the suspension. It is used for various purposes, such as
      to estimate the number of bacteria in suspension in a
      liquid.
      [PJC]