n Son of the same parents as another person.
n A male having at least one parent in common with another (see half-brother, stepbrother).
n A male fellow member of a religious community, church, trades union etc.
n (informal) A form of address to a man.
n (African-American Vernacular) A fellow black man.
n Somebody, usually male, connected by a common cause, situation, or affection.
n Someone who is a peer, whether male or female.
n (poetic) Someone who is a kinsman or shares the same patriarch.
v (transitive) To treat as a brother.
n Title of respect for an adult male member of a religious or fraternal order.
n Title of respect for an adult male member of a fraternal/sororal organization, or comrade in a movement, or even a stranger using fictive kin.
n A title used to personify or respectfully refer to concepts or animals.