Tucks tail is an idiomatic expression that refers to a submissive or cowardly behavior. There are several synonyms for this phrase that can be used interchangeably, such as backing down, cowering, cringing, flinching, yielding, retreating, submitting, surrendering, or bowing. These synonyms imply a sense of fear, intimidation, or defeat, suggesting that the person is unwilling to stand up for themselves or lacks confidence in the situation. It is important to note that the use of these synonyms should be considered within the context of the situation and the intended meaning of the expression, as each word carries a slightly different connotation.