The word "out-rival" refers to surpassing, outdoing, or excelling someone or something. Its antonyms would thus be words that mean the opposite, such as underperform, fall behind, fail, lag, or lose. Out-rival implies competition and success, so its antonyms often connote defeat or mediocrity. For example, instead of out-rivaling someone, one might trail behind or fail to measure up. The antonyms of out-rival might also suggest different approaches or values, such as cooperation or humility rather than striving for superiority. Ultimately, the antonyms of out-rival can help us consider alternative paths to success and draw attention to the value of collaboration, growth, and equality over competition.