There are several synonyms for the phrase "puts one's tail between one's legs." One of them is "back down," which means to withdraw from a confrontation or dispute. Another synonym is "retreat," which means to withdraw or move back from a dangerous or difficult situation. "Submit" is also a synonym, meaning to accept or yield to someone or something. "Surrender" is another option, which means to give up or hand over control or power. Lastly, "apologize" is a synonym, suggesting that one has admitted they were wrong and expressed regret for their actions or words. All of these synonyms convey the idea of admitting defeat or accepting responsibility for one's actions.