Yuen \Yu"en\, n. (Zo["o]l.) The crowned gibbon (Hylobates pileatus), native of Siam, Southern China, and the Island of Hainan. It is entirely arboreal in its habits, and has very long arms. the males are dark brown or blackish, with a caplike mass of long dark hair, and usually with a white band around the face. The females are yellowish white, with a dark spot on the breast and another on the crown. Called also wooyen, and wooyen ape.

Source: Webster's Revised Unabridged Dictionary (1913)