Every time I ask him for the truth, he tries to weasel around the question.

weasel 本义是"黄鼠狼"，在英语中常用来比喻"狡猾、逃避责任的人"。 weasel around 是固定搭配，字面意思是"像黄鼠狼一样绕来绕去"，引申为"逃避问题、闪烁其词"的行为。