Source : Webster's Revised Unabridged Dictionary (1913)

Overcoat \O"ver*coat`\, n. [Cf. {Surcoat}.]
   A coat worn over the other clothing; a greatcoat; a topcoat.

Source : WordNet®

overcoat
     n 1: a heavy coat worn over clothes in winter [syn: {greatcoat},
          {topcoat}]
     2: an additional protective coating (as of paint or varnish)
        [syn: {overcoating}]