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]