1. relatively advanced physically, mentally, emotionally, etc.; grown-up
2. (of plans, theories, etc.) fully considered; perfected
3. due or payable: a mature debenture
a. fully developed or differentiated: a mature cell
b. fully grown; adult: a mature animal
5. (of fruit, wine, cheese, etc.) ripe or fully aged
6. youthful See also old (of a river valley or land surface) in the middle stage of the cycle of erosion, characterized by meanders, maximum relief, etc.
7. to make or become mature