Source : Webster's Revised Unabridged Dictionary (1913)

Loon \Loon\, n. [For older loom, Icel. l?mr; akin to Dan. & Sw.
   lom.] (Zo["o]l.)
   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 ({U.
   septentrionalis}), are the best known species. See {Diver}.

Diver \Div"er\, n.
   1. One who, or that which, dives.

            Divers and fishers for pearls.        --Woodward.

   2. Fig.: One who goes deeply into a subject, study, or
      business. ``A diver into causes.'' --Sir H. Wotton.

   3. (Zo["o]l.) Any bird of certain genera, as {Urinator}
      (formerly {Colymbus}), or the allied genus {Colymbus}, or
      {Podiceps}, remarkable for their agility in diving.

   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}.