bro.

Noun

brother (plural brothers or (archaic in most senses) brethren)

1. Son of the same parents as another person.
   • It was a joy to snatch some brief respite, and find himself in the rectory drawing–room. Listening here was as pleasant as talking; just to watch was pleasant. The young priests who lived here wore cassocks and birettas; their faces were fine and mild, yet really strong, like the rector's face; and...1918, W[illiam] B[abington] Maxwell, chapter X, in The Mirror and the Lamp, Indianapolis, Ind.: The Bobbs-Merrill Company, →OCLC
2. A male having at least one parent in common with another person (see half-brother, stepbrother).
3. A male fellow member of a religious community, church, trades union etc.
   • You shall not charge interest to your brother—interest on money or food or anything that is lent out at interest.1975, New King James Version, Deuteronomy 23:19
4. (informal) A form of address to a man.
   • Brother, can you spare a dime?
5. (African-American Vernacular) A fellow black man.
   • [Michael Jackson] went on television and said, “I don't have sex because of my religious beliefs”, and the public believed it. I know brothers was like “get the fuck out of here!”. And white people, “Michael's a special kinda guy!”1987, Eddie Murphy Raw, spoken by Eddie Murphy
6. Somebody, usually male, connected by a common cause, situation, or affection.
   • The marvelous new militancy which has engulfed the Negro community must not lead us to a distrust of all white people, for many of our white brothers, as evidenced by their presence here today, have come to realize that their destiny is tied up with our destiny.1963, Martin Luther King Jr., (Please provide the book title or journal name)

See all 13 meanings of brother