found: Merriam Webster online dictionary(icebreaker; first entered, 1875; a ship equipped (as with a reinforced bow) to make and maintain a channel through ice)
found: Gentile, Gary, Nautical cyclopedia, 1995(usage: icebreaker)
found: Aak to Zumbra, a dictionary of the world's watercraft, c2000(usage, ice breaker)
found: Wikipedia, July 28, 2008:icebreaker article (An icebreaker is a special purpose ship or boat designed to move and navigate through ice-covered waters. Although the term usually refers to icebreaking ships, it can also refer to smaller vessels (e.g., icebreaking boats))