讓某人捉摸不定(或猜不透)
keep sb guessing
to not tell sb about your plans or what is going to happen next
It's the kind of book that keeps you guessing right to the end.這是一本讓你從頭猜到尾的書。
釋義來自《牛津高階英漢雙解詞典》第 9 版