What is retention ? Retention is the act of retaining, that is, holding onto or keeping possession of something, as in Kim noted the plant’s successful retention of water. Retention is also used to refer to the state of being retained or having the power to retain something, as in The lawyer was outraged by the police’s continued retention of ... Retention of clients or money is the process of ensuring that a policyholder remains a customer of the insurer or that money to be paid out remains in the insurer's accounts. Definition of retention noun in Oxford Advanced Learner's Dictionary. Meaning , pronunciation, picture, example sentences, grammar, usage notes, synonyms and more. Define retention . retention synonyms, retention pronunciation, retention translation, English dictionary definition of retention . n. 1. The act of retaining or the condition of being retained: the retention of nutrients in the soil; the retention of jobs in the city. 2. The practice of...