He vacillated between two explanations for a year, until a single new measurement ruled one of them out.
他在两种解释之间摇摆了一年，直到一次新测量排除了其中之一。
Which choice best defines “vacillate”?
D — To waver; be indecisive.. “vacillate” means To waver; be indecisive..
Which word means “To waver; be indecisive.”?
A — vacillate. “vacillate” means To waver; be indecisive..
vacillate — To waver; be indecisive.. In Chinese: 摇摆；犹豫不决.
vacillate is pronounced //ˈvæsɪleɪt//.
He vacillated between two explanations for a year, until a single new measurement ruled one of them out. (他在两种解释之间摇摆了一年，直到一次新测量排除了其中之一。)
waver, hesitate, dither — all close in meaning to vacillate (To waver; be indecisive.).
decide, commit — each the opposite of vacillate (To waver; be indecisive.).
Yes. vacillate is on the SAT Prep Difficult list — the higher-register words that decide the hard questions. The Digital SAT does not test vocabulary in isolation; words like this one are tested through Words in Context questions, where you choose the word that completes a passage most logically and precisely.
vacill(摇摆) → 拿不定主意。