巨嬰

巨婴
jùyīng
(neologism c. 2017) adult who behaves in a childish manner (e.g. throwing a tantrum)

CEDICT

neologism

Entry Composition

=1 巨 jù
  1. very large; huge; tremendous; gigantic
  2. (coll.) very; extremely
=1 巨 jù variant of 巨 jù
2 嬰 yīng
  1. infant
  2. baby