imponderable
noun [ C ] formal uk/ɪmˈpɒn.dər.ə.bəl/ us/ɪmˈpɑːn.dər.ə.bəl/
（效果或结果）无法预测（或估量）的
something that cannot be guessed or calculated because it is completely unknown
There are too many imponderables to make an accurate forecast. 无法估量的事情太多，因而难以作出准确的预测。