inexplicable
adj. 费解的；无法说明的；不能解释的
例句
For some inexplicable reason he gave up a fantastic job.
由于某种莫名其妙的原因，他放弃了一份很不错的工作。
《牛津词典》
His behaviour was extraordinary and inexplicable.
他的行为离奇且令人费解。
《柯林斯英汉双解大词典》
It was an odd stance, but not inexplicable.
这虽然奇怪，但却并非不可解释。
