The phrase "tucking tail" means to retreat or run away from a situation in fear or defeat. There are many synonyms that can be used to convey this same idea, including "scared off," "fleeing," "withdrawing," "backing down," "cowering," "retreating," "slinking away," "taking flight," "quitting," and "yielding." Each of these words can be used to describe someone who is unwilling or unable to face a challenge, and may convey different levels of intensity or emotional impact. Whether it's a physical battle or a social confrontation, there are many ways to describe the act of "tucking tail" and running away.