Brother- Definition:brotháer [br??r] noun (plural brotháers) 1. male sibling: a boy or man who has the same father and mother as another person 2. or (plural brotháers or bretháren [br?r?n]) fellow member: a man who belongs to the same ethnic group, religion, profession, trade, or organization as another man fraternity brothers 3. close male friend: used to address a close male friend 4. or (plural brotháers or bretháren) christianity lay member: a member of a religious order for men 5. or (plural brotháers or bretháren) christianity devoted religious worker: a man who devotes himself to the work of a men’s religious order without having been professed [ Old English br??or < Indo-European]