(1) Any agreement between two or more parties that establishes a legal obligation. (2) The act of carrying out such an obligation. (3) All activities affecting a deposit account that are performed at the request of the account holder. (4) All events that cause some change in the assets, liabilities or net worth of a business. (5) An action between a cardholder and a merchant or a cardholder and a member that results in activity on the cardholder account.