A buoy, often unlighted, used as a replacement for a light buoy or a large unlighted buoy in certain areas during the winter months when other aids to navigation are temporarily withdrawn.
The term ice buoy is used when the buoy is designed to withstand the effects ofice.
In German, the term Winterbetonnung means the state of the buoyage system as modified during the winter months.
The French term "bouee d'hiver" is not much used in France.
Please note that this is the term as it stands in the original IALAInternational Association of Marine Aids to Navigation and Lighthouse Authorities - AISM Dictionary edition (1970-1989)