Pronunciation: (in'fun-tl-iz"um, -tī-liz"-, in-fan'tl-iz"um),[key] —n. 1. the persistence in an adult of markedly childish anatomical, physiological, or psychological characteristics.
2. an infantile act, trait, etc., esp. in an adult.
3. a speech disorder characterized by speech and voice patterns that are typical of very young children.