Ring-necked \Ring"-necked`\, a. (Zo["o]l.) Having a well defined ring of color around the neck. {Ring-necked duck} (Zool.), an American scaup duck ({Aythya collaris}). The head, neck, and breast of the adult male are black, and a narrow, but conspicuous, red ring encircles the neck. This ring is absent in the female. Called also {ring-neck}, {ring-necked blackhead}, {ringbill}, {tufted duck}, and {black jack}.