CHILDISH
childish, infantile
(adjective) indicating a lack of maturity; “childish tantrums”; “infantile behavior”
Source: WordNet® 3.1
Etymology
Adjective
childish (comparative more childish, superlative most childish)
Of or suitable for a child.
Behaving immaturely.
Synonyms
• (suitable for a child): childly, juvenile, kiddish; see also childlike
• (behaving immaturely): infantile, immature, silly, unbecoming, juvenile, puerile; see also childish
Antonyms
• (suitable for a child): adult, adultlike
• (behaving immaturely): adultish, mature
Source: Wiktionary
Child"ish, a.
1. Of, pertaining to, befitting, or resembling, a child. "Childish
innocence." Macaulay.
2. Peurile; trifling; weak.
Methinks that simplicity in her countenance is rather childish than
innocent. Addison.
Note: Childish, as applied tc persons who are grown up, is in a
disparaging sense; as, a childish temper.
Source: Webster’s Unabridged Dictionary 1913 Edition