Any one of numerous species of beetles belonging to
   Gyrinus and allied genera. The body is firm, oval or boatlike in form,
   and usually dark colored with a bronzelike luster. These beetles live
   mostly on the surface of water, and move about with great celerity in a
   gyrating, or circular, manner, but they are also able to dive and swim
   rapidly. The larva is aquatic. Called also weaver, whirlwig, and
   whirlwig beetle.