impugn /ɪmˈpjuːn/ ( impugning, impugned, impugns )

• 1. 

  V-T If you impugn something such as someone's motives or integrity, you imply that they are not entirely honest or honourable. 指责; 质疑 [正式]

  例：

  The Secretary's letter impugns my motives.

  该部长的来函质疑我的动机。