Definition of union

• an organization of employees formed to bargain with the employer; "you have to join the union in order to get a job"
• the United States (especially the northern states during the American Civil War); "he has visited every state in the Union"; "Lee hoped to detach Maryland from the Union"; "the Norths superior resources turned the scale"
• the act of pairing a male and female for reproductive purposes; "the casual couplings of adolescents"; "the mating of some species occurs only in the spring"