The word "outgrow" means to become too big for something or to mature past a certain stage. There are several synonyms that can be used in place of "outgrow," including "surpass," "exceed," "transcend," "progress beyond," "mature beyond," "evolve past," "move past," "advance beyond," and "developmentally surpass." These synonyms can be used in various contexts, such as in personal growth, academic achievements, and physical size. Using different synonyms can add variety to the language and make the writing or conversation more interesting. Choosing the appropriate synonym depends on the situation and context in which it is used.