impeach

Short definition from Wiktionary

Verb

1. 1
   To hinder, impede, or prevent.
2. 2
   To bring a legal proceeding against a public official.
3. 3
   To charge with impropriety; to discredit; to call into question.
4. 4
   To demonstrate in court that a testimony under oath contradicts another testimony from the same person, usually one taken during deposition.