The Collaborative International Dictionary of English v.0.48:

Snowplow \Snow"plow`\, Snowplough \Snow"plough`\, n.
   An implement operating like a plow, but on a larger scale,
   for clearing away the snow from roads, railways, etc.
   [1913 Webster]

WordNet (r) 3.0 (2006):

snowplow
    n 1: a vehicle used to push snow from roads [syn: snowplow,
         snowplough]