brother

Concise Oxford English Dictionary © 2008 Oxford University Press:
brother/ˈbrʌðə(r)/

▶noun

• 1 a man or boy in relation to other sons and daughters of his parents.

• 2 a male associate or fellow member of an organization.

• 3 N. Amer. informal a black man.

• 4 something which resembles or is equivalent to another.

• 5 (pl. also brethren) Christian Church a (male) fellow Christian.

  ■ a member of a religious order of men.

▶exclamation chiefly N. Amer. used to express annoyance or surprise.

– derivatives
brotherliness noun,
brotherly adjective.

– origin OE brōthor, of Gmc origin.