Definitions

1. noun

an animal, especially a mammal, that has reached a stage of development beyond the juvenile stage but has not yet reached full maturity

“The zookeeper noted that the subadult rhinoceros was growing rapidly and would soon reach its full size.”

2. adjective

relating to or being in a stage of development that is beyond the juvenile stage but has not yet reached full maturity

“The subadult characteristics of the young bird’s plumage were still visible, even as it prepared for its first molt.”