Noun
1. a male with the same parents as someone else;
"my brother still lives with our parents"2. a male person who is a fellow member (of a fraternity or religion of other group);
"none of his brothers would betray him"3. a close friend who accompanies his buddies in their activities
4. used as a term of address for those male persons engaged in the same movement;
"Greetings, comrade!"