picket ship(n = noun.artifact) - a ship serving as a picket;
is a kind of picket
abandoned ship, about ship, capital ship, cargo ship, clipper ship, combat ship, container ship, cruise ship, dress ship, factory ship, fire ship, gas-turbine ship, guard ship, hospital ship, liberty ship, merchant ship, nuclear-powered ship, passenger ship, patrol ship, picket, picket boat, picket fence, picket line, pirate ship, sailing ship, school ship, ship, ship biscuit, ship broker, ship builder, ship canal, ship chandler, ship money, ship of the line, ship railway, ship route, sister ship, slave ship, small ship, supply ship, surface ship, tank ship, training ship, transport ship, treasure ship, wear ship, weather ship, whaling ship