picketboat
/ˈpɪkɪt boʊt/
noun
- A small boat used for patrolling or guarding a harbor, coastline, or naval formation, often as a sentry or to enforce regulations.
- A picketboat circled the anchored fleet to ensure no unauthorized boats approached.
- The harbor master sent a picketboat to check on the suspicious vessel.
- The coast guard used a picketboat to monitor the busy shipping channel.