Adultoid

An adultoid is a mature alate that remains in the colony, sheds its wings and becomes a functional reproductive.

Source: wiktionary

Greenberger and Steinberg coined the term “adultoid” to describe adolescents who engage in activities, often “risky” activities, that symbolize adult status (e.g., smoking, drinking, staying out late, having sex).

Source: wiktionary

This link between an older subjective age and engagement in problem behaviors supports the existence of adultoid or pseudomature adolescents who have been described in theoretical literature, but until recently, remained unidentified empirically.

Source: wiktionary

Personal conversations I had with teachers/counsellors in different high schools responsible for overseeing RAP certainly indicated that, at least initially, students' confidence about their newly discovered sense of maturity was closer to pseudomaturity or adultoid behaviour.

Source: wiktionary