1. The money was lent for an undefined period of time. 这笔钱无限期借出。
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. 这个不确定的背景也显示了塞西莉亚·波克斯是如何受到法国印象派画家的影响的，他们和波克斯一样赞同用个人而非传统的方法来处理主题对象。
4. The method XXX is undefined for the type yyy. xxx方法对于类型yyy来说定义不明确。
5. Undefined reference, what was the solution last time? 未定义的引用，上次我们是怎么解决的呢？
