Source : Webster's Revised Unabridged Dictionary (1913)

Infantile \In"fan*tile\ (?; 277), a. [L. infantilis: cf. F.
   infantile. See {Infant}.]
   Of or pertaining to infancy, or to an infant; similar to, or
   characteristic of, an infant; childish; as, infantile
   behavior.

Source : WordNet®

infantile
     adj 1: indicating a lack of maturity; "childish tantrums";
            "infantile behavior" [syn: {childish}]
     2: of or relating to infants or infancy; "infantile paralysis"
     3: being or befitting or characteristic of an infant;
        "infantile games"