The term "intellectually childish" refers to someone who displays a lack of maturity in their thinking or reasoning. There are several synonyms for this phrase, including "mentally immature," "cognitively undeveloped," "naive," "immature in judgment," "intellectually stunted," "unwise," "uninformed," and "inexperienced." These words all imply a certain level of immaturity in one's ability to make sound decisions and think critically. They are often used to describe individuals who make poor choices or exhibit behavior that is unbecoming of their age or position. By using these synonyms, we can accurately convey the notion of intellectual childishness in a more precise and nuanced manner.