Real Dictionary

buoy
countable noun: A buoy is a floating object that is used to show ships and boats where they can go and to warn them of danger.
verb: If someone in a difficult situation is buoyed by something, it makes them feel more cheerful and optimistic.

buoy in American English
a floating object anchored in a lake, river, etc. to mark a channel, warn of a hazard, etc., variously shaped and colored, and often equipped with a bell or light
intransitive verb: to float or rise by reason of lightness
noun: a distinctively shaped and marked float, sometimes carrying a signal or signals, anchored to mark a channel, anchorage, navigational hazard, etc., or to provide a mooring place away from the shore
transitive verb: to keep afloat or support by or as if by a life buoy; keep from sinking

buoy in British English
noun: a distinctively shaped and coloured float, anchored to the bottom, for designating moorings, navigable channels, or obstructions in a body of water