infantilism

詳細解釋：

in.fan.til.ism

n.（名詞）
A state of arrested development in an adult, characterized by retention of infantile mentality, accompanied by stunted growth and sexual immaturity, and often by dwarfism.
幼稚病：一種出現於成年人當中的發育停滯的狀態，其特點是思維幼稚，伴有發育不良和性方面的不成熟，還有侏儒現象發生

Extreme immaturity, as in behavior or character:
幼稚型：如在行為或性格上表現的特別不成熟：
例句：
.infantilism, which is the subtext of so much American cinema and culture.(John Simon)
.幼稚病是許多美國電影和文化的特徵.(約翰·西蒙)

An infantile act or remark.
幼稚行為：幼稚的行為或言論