BUOY

v. keep afloat; support, sustain, encourage

n. anchored float used as a guide to navigators

A buoy is a floating device that can have many different purposes, which determine whether the buoy is anchored (stationary) or allowed to drift. The word is most commonly pronounced (as in buoyant), but in American English it is often pronounced .
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Noun
1. bright-colored; a float attached by rope to the seabed to mark channels in a harbor or underwater hazards
(hypernym) reference point, point of reference, reference
(hyponym) acoustic buoy
Verb
1. float on the surface of water
(hypernym) float, swim
2. keep afloat; "The life vest buoyed him up"
(synonym) buoy up
(hypernym) hold, support, sustain, hold up
3. mark with a buoy
(hypernym) mark

(v. t.)
To support or sustain; to preserve from sinking into ruin or despondency.
  

(v. t.)
To keep from sinking in a fluid, as in water or air; to keep afloat; -- with up.
  

(v. t.)
To fix buoys to; to mark by a buoy or by buoys; as, to buoy an anchor; to buoy or buoy off a channel.
  

(v. i.)
To float; to rise like a buoy.
  

(n.)
A float; esp. a floating object moored to the bottom, to mark a channel or to point out the position of something beneath the water, as an anchor, shoal, rock, etc.
  

A float moored or anchored in water. (DOI4)