The phrase "thresh about" typically means to move erratically or with great agitation. There are a number of synonyms that can be used to convey a similar meaning, including flail, flounder, thrash, toss and turn, and writhe. Each of these verbs connotes a sense of frenzied or uncontrolled motion, often suggesting a struggle or lack of coordination. Depending on the specific context in which "thresh about" is used, any of these synonyms might be appropriate to capture the intended meaning of the phrase. By choosing a different word with a similar meaning, writers and speakers can add variety and nuance to their language, while still conveying the necessary information.