髯 is a bound form (b.f.) meaning 'side-whiskers' or 'sideburns' — the hair that grows on the sides of a man's face, between the ears and the beard. It almost never appears alone in modern Chinese; you'll see it in literary or descriptive compounds like 髯口 (the fake beard in traditional opera) or in classical texts describing a man's facial hair. For everyday modern speech, use 胡子 for beard/mustache or 络腮胡 for full side-whiskers.