Source : Webster's Revised Unabridged Dictionary (1913)

Smokestack \Smoke"stack`\, n.
   A chimney; esp., a pipe serving as a chimney, as the pipe
   which carries off the smoke of a locomotive, the funnel of a
   steam vessel, etc.

Source : WordNet®

smokestack
     n : a large tall chimney through which combustion gases and
         smoke can be evacuated [syn: {stack}]