The word "outgrew" indicates an act of surpassing or outpacing something or someone. There are several synonyms that can be used in place of "outgrew" that can convey a similar meaning. For example, "outmatched," "outclassed" and "outstripped" are all expressions that signify exceeding someone or something. "Overshadowed," "eclipsed" and "overtook" are also popular synonyms used to describe outdoing a competitor. Finally, "overcame," "surmounted" and "conquered" can be used to describe the process of overcoming a challenge or obstacle that was previously insurmountable. Regardless of which synonym is used, the general idea is that something has been surpassed or exceeded in some way.