Mature definition, complete in natural growth or development, as plant and animal forms a mature rose bush. Mature people behave like adults in a way that shows they are well developed emotionally 2. 19 synonyms of mature from the merriam-webster thesaurus, plus 68 related words, definitions, and antonyms. Mature synonyms, mature pronunciation, mature translation, english dictionary definition of mature. Having reached full natural growth or development a mature cell. Mature definition the definition of mature refers to someone or something that is full grown or adult, either physically or in terms of behavior and attitude. (adjective) an example of mature is someone who behaves appropriately and doesnt throw. the term mature student is usually used when referring to anyone going to university or college after a period of time out of full-time education. Typically, this will mean students who are over 21 years of age at the beginning of their undergraduate studies, or over 25 years of age at the beginning of their postgraduate studies. A mature technology is a technology that has been in use for long enough that most of its initial faults and inherent problems have been removed or reduced by further development. In some contexts, it may also refer to technology that has not seen widespread use, but whose scientific background is well understood. Its performance characteristics are also expected to be well understood with. The quality of behaving mentally and emotionally like an adult 2.