n. A male person, in his relation to another person or other persons of either sex born of the same parents; a male relative in the first degree of descent or mutual kinship: used also of the lower animals: the converse of sister. See brother-in-law and half-brother.n. A male person in his relation to any other person or persons of the same blood or ancestry; a member of a common family or race in his relation to all other members; in the plural, all members of a particular race, or of the human race in general, as regards each other.n. One of two or more men closely united without regard to personal kinship, as by a common interest; an associate; one of the same rank, profession, occupation, or belief, especially in law, religion, or organized charity.n. Specifically, as a translation of friar, a member of a mendicant order.n. In the plural form brethren, the designation of several Christian organizations, derived from the fact that the title was used by the primitive Christians in speaking of themselves; specifically, a sect of German Baptists, more popularly known as Dunkers.n. A member of a religious congregation whose members do not receive the priesthood, but devote themselves to teaching or good works; also, a lay member of a community having priests.n. Figuratively, one who resembles another in manners or disposition.n. Often abbreviated bro., plural bros.n. [The plural form brethren is not now used in the sense of male children of the same parents, but only in the wider meanings of the word brother.]Bearing a fraternal relation in a general sense; of the character of a brother: as, a brother man or magistrate.To consider or treat as a brother; address as a brother.To relate as brothers; make kin.