The Collaborative International Dictionary of English v.0.48:

iceboat \iceboat\ n.
   1. A ship with a reinforced bow to break up ice and keep
      channels open for navigation; an icebreaker.

   Syn: icebreaker.
        [WordNet 1.5]

   2. a sailing craft with runners and a cross-shaped frame;
      suitable for traveling over ice; it is usually propelled
      by a sail, and sometimes by an engine-powered propeller.

   Syn: ice yacht.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

iceboat
    n 1: a ship with a reinforced bow to break up ice and keep
         channels open for navigation [syn: icebreaker, iceboat]
    2: a sailing vessel with runners and a cross-shaped frame;
       suitable for traveling over ice [syn: iceboat, ice yacht,
       scooter]