Nonretentive is a word that is used to describe a lack of ability to retain or maintain. There are several synonyms available for the term nonretentive, which include forgetful, unretentive, leaky and sieve-like. These synonyms are used to describe conditions where someone is unable to retain information, memory, data or even liquid. Forgetful refers to a person who is not able to retain memory for an extended period, while the term unretentive describes something that doesn't retain things for a long period. Leaky, on the other hand, is used to describe a physical object that loses liquid while sieve-like is used to signify something that lets things pass through in an uncontrolled manner.