INFANTILE
childish, infantile
(adjective) indicating a lack of maturity; “childish tantrums”; “infantile behavior”
infantile
(adjective) being or befitting or characteristic of an infant; “infantile games”
infantile
(adjective) of or relating to infants or infancy; “infantile paralysis”
Source: WordNet® 3.1
Etymology
Adjective
infantile (comparative more infantile, superlative most infantile)
Pertaining to infants.
Childish; immature.
Synonyms
• (childish): puerile, milky; see also childish
Source: Wiktionary
In"fan*tile, a. Etym: [L. infantilis: cf. F. infantile. See Infant.]
Definition: Of or pertaining to infancy, or to an infant; similar to, or
characteristic of, an infant; childish; as, infantile behavior.
Source: Webster’s Unabridged Dictionary 1913 Edition