noun see: thin Date: 1901 retention of some larval or immature characters in adulthood, attainment of sexual maturity during the larval stage, neotenic adjective
NEOTENY
Meaning of NEOTENY in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012