The word "out rivalled" implies excelling or surpassing someone or something. Its antonyms, on the other hand, indicate inferiority, weakness or falling short. Some of the phrases which can be used as antonyms for "out rivalled" include underperformed, lagged behind, lost, fell short, and was outdone. For instance, if a sports team failed to win a game, you could say that they underperformed or fell short of expectations. Similarly, if a company's revenue declined, you could say that they lost ground to their competitors. The antonyms for "out rivalled" highlight the importance of competitiveness and maintaining high standards.