Vacillation is the noun for what a person does when they vacillate — the state of changing your mind again and again and not settling on anything. You can use it uncountably, for the general behaviour (his vacillation cost us the deal), or countably in the plural, for the separate wobbles (after several vacillations, she signed). The uncountable use is far more common. Like the verb, it is formal and it is usually a criticism. Newspapers love it for politicians and leaders: "weeks of vacillation", "the government's vacillation over the border rules". The message underneath is almost always "they should have decided by now, and their not deciding is causing harm". In ordinary speech, people would say "he kept changing his mind", "all this back and forth", or "dithering". Save vacillation for writing, and for when you want a serious tone. It often appears with words that measure it — endless vacillation, constant vacillation, months of vacillation — and with "over", "about", or "between": vacillation over the budget, vacillation between the two plans.

猶豫不決、搖擺（名詞）。指反覆改變決定、遲遲不下決斷的那種狀態，常用來批評領導者或政府。