VERB + IMMATURELY
behaving, hatched
IMMATURELY + NOUN
teenager
ADV.
immediately
adv
Giving an appearance of immaturity; childishly.
They may be approaching 40, but after three beers they are behaving as immaturely as any teenager.
Without having attained maturity.
[…] birds which are hatched immaturely and fly immediately after leaving the nest.
adverb — in an immature manner