1. (Science: zoology) Any one of numerous species of large aquatic birds belonging to Cygnus, Olor, and allied genera of the subfamily Cygninae. They have a large and strong beak and a long neck, and are noted for their graceful movements when swimming. most of the northern species are white. In literature the swan was fabled to sing a melodious song, especially at the time of its death.
The European white, or mute, swan (Cygnus gibbus), which is most commonly domesticated, bends its neck in an S-shaped curve. The whistling, or trumpeting, swans of the genus Olor do not bend the neck in an S-shaped curve, and are noted for their loud and sonorous cry, due to complex convolutions of the windpipe. To this genus belong the European whooper, or whistling swan (Olor cygnus), the American whistling swan (O. Columbianus), and the trumpeter swan (O. Buccinator). The Australian black swan (Chenopis atrata) is dull black with white on the wings, and has the bill carmine, crossed with a white band. It is a very graceful species and is often domesticated. The south American black-necked swan (Sthenelides melancorypha) is a very beautiful and graceful species, entirely white, except the head and neck, which are dark velvety seal-brown. Its bill has a double bright rose-coloured knob.
3. (Science: astronomy) The constellation Cygnus.
Origin: AS. Swan; akin to D. Zwaan, OHG. Swan, G. Schwan, Icel. Svanr, Sw. Svan, Dan. Svane; and perhaps to E. Sound something audible.