The money was lent for an undefined period of time.
这笔钱无限期借出。
《牛津词典》
2
A sort of undefined longing crept upon them.
一种莫名的渴望爬上了他们的心头。
3
The undefined background also shows how Cecilia Beaux was influenced by the French Impressionists, who believed, like Beaux, in a personal rather than conventional approach to their subject matter.