Hebephrenic is an adjective that is used to describe someone who has a juvenile or child-like personality. This word is often used in the field of psychiatry to describe someone who has a disorder that makes them act in a childish or immature way. Some synonyms for hebephrenic include puerile, infantile, and immature. Other synonyms for those who have a mental disorder with symptoms of silliness and odd behavior include zany, wacky, and eccentric. These words can be used to describe someone who is acting in an unusual or peculiar way and may also be associated with a mental disorder.