The Biden Emails Prove Impeachment Was A Sham. The New York Post story shows once and for all that Trump's impeachment was all based on a lie. October 17, 2020 By David Marcus. prove (pro͞ov) v. proved, proved or prov·en (pro͞o′vən), prov·ing, proves . 1. a. To establish the truth or validity of (something) by the presentation of argument or evidence: The novel proves that the essayist can write in more than one genre. The storm proved him to be wrong in his prediction. b. To demonstrate the reality of (something