n. 1 a man or boy in relation to other sons and daughters of his parents. 2 a (often as a form of address) a close male friend or associate. b a male fellow member of a trade union etc. 3 (pl. also brethren) a a member of a male religious order, esp. a monk. b a fellow member of the Christian Church, a religion, or (formerly) a guild etc. 4 a fellow human being. brother german see GERMAN. brother-in-law (pl. brothers-in-law) 1 the brother of one's wife or husband. 2 the husband of one's sister. 3 the husband of one's sister-in-law. brother uterine see UTERINE 2. brotherless adj. brotherly adj. & adv. brotherliness n.
[ OE brothor f. Gmc ]