from the GNU version of the Collaborative International Dictionary of English
- n. A boat used by harbor authorities to enforce the observance of quarantine regulations.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a boat that is on guard duty (as in a harbor) around a fleet of warships
Sorry, no etymologies found.
The guard boat hove to under the Kittys quarter, presumably because she was the ship showing the signal flags, and was therefore deemed to be the ship in command of the small convoy.