Learner's definition of BROTHER
1 : a boy or man who has one or both of the same parents as you 2 : a man who is from the same group or country as you 3 pluralbrothers; orbrethren/ˈbrɛðrən/ : a male member of a religious group— used especially as a title 4 US, informal : a black man— used especially by African-Americans 5 US, informal — used when talking to a man
Brother, do you have an extra cigarette?
Brother, you have got to relax.
6 chiefly US, informal — used as an interjection to express surprise or annoyance