indefinable
adj. 难下定义的；难确定的；模糊不清的
n. 难下定义的事物；难以确切描述的事物
例句
There was something indefinable in her eyes.
她的眼神里有种难以形容的东西。
《柯林斯英汉双解大词典》
She has that indefinable something that makes an actress a star.
她具备了那种使演员成为明星的说不出的特质。
《牛津词典》
Some mysterious, indefinable characteristic sets him apart from all other men.
某些神秘的，难以确切描述的特性令这样的人卓尔不群。
