To support or maintain at a high level.
To maintain or enhance enthusiasm or confidence; to lift the spirits of.
To keep afloat or aloft; used with up.
To mark with a buoy.
A life-buoy; a life preserver.
A float moored in water to mark a location, warn of danger, indicate a navigational channel or for other purposes
To act as a flagship for.
The most important one out of a related group.
The ship occupied by the fleet's commander (usually an admiral); it denotes this by flying his flag.
The ship regarded as most important out of a group, e.g. a nation's navy or company's fleet.