1. The state of being a partner.
2. a. A legal contract entered into by two or more persons in which each agrees to furnish a part of the capital and labor for a business enterprise, and by which each shares a fixed proportion of profits and losses.
b. The persons bound by such a contract.
3. A relationship between individuals or groups that is characterized by mutual cooperation and responsibility, as for the achievement of a specified goal: Neighborhood groups formed a partnership to fight crime.