1 (navigational or channel) mark or marker, float; nun (-buoy), can (-buoy), bell (buoy), gong (-buoy), siren, signal, mooring-buoy, spar-buoy, lollipop:
Returning to port, always leave the red buoys to starboard.
2 Often, buoy up. lift, raise, elevate, support, hearten, sustain, keep up:
We sang songs to buoy up our spirits while the rescuers dug their way towards us.