knife-edge

柯林斯詞典

1. PHRASE To be on a knife-edge means to be in a situation in which nobody knows what is going to happen next, or in which one thing is just as likely to happen as another. 形勢難料; 撲朔迷離[oft v-link PHR]
The game is poised on a knife-edge. One mistake or one piece of good luck could decide it. 比賽形勢撲朔迷離。一個失誤或是一點運氣就有可能決定勝負。
2. ADJ You can use knife-edge to refer to something that is very exciting or tense because you do not know what is going to happen next. 難以預料的[ADJ n]
Tonight's knife-edge vote could be uncomfortably close. 今晚的投票難以預料，結果可能會很接近，真令人緊張。