Loon \Loon\, n. [For older loom, Icel. l[=o]mr; akin to Dan. &
   Sw. lom.] (Zool.)
   Any one of several aquatic, wed-footed, northern birds of the
   genus Urinator (formerly Colymbus), noted for their
   expertness in diving and swimming under water. The common
   loon, or great northern diver (Urinator imber, or Colymbus
   torquatus), and the red-throated loon or diver (Urinator
   septentrionalis), are the best known species. See Diver.
   [1913 Webster]

Diver \Div"er\, n.
   1. One who, or that which, dives.
      [1913 Webster]

            Divers and fishers for pearls.        --Woodward.
      [1913 Webster]

   2. Fig.: One who goes deeply into a subject, study, or
      business. "A diver into causes." --Sir H. Wotton.
      [1913 Webster]

   3. (Zool.) Any bird of certain genera, as Urinator
      (formerly Colymbus), or the allied genus Colymbus, or
      Podiceps, remarkable for their agility in diving.
      [1913 Webster]

   Note: The northern diver (Urinator imber) is the loon; the
         black diver or velvet scoter (Oidemia fusca) is a sea
         duck. See Loon, and Scoter.
         [1913 Webster]