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.
Phrases and idioms:
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.
Derivatives:
brotherless adj. brotherly adj. & adv. brotherliness n.
Etymology: OE brothor f. Gmc