buoy

Short definition from Wiktionary

Noun

1. 1
   A float moored in water to mark a location, warn of danger, indicate a navigational channel or for other purposes
2. 2
   A float moored in water to mark a location, warn of danger, indicate a navigational channel or for other purposes: A lifebuoy; a life preserver.
3. 3
   A sign where the non-dominant hand is held in a stationary configuration as a landmark for meaning associations with the dominant hand.

Verb

1. 1
   To keep afloat or aloft; used with up.
2. 2
   To support or maintain at a high level.
3. 3
   To mark with a buoy.
4. 4
   To maintain or enhance enthusiasm or confidence; to lift the spirits of.