Definitions of impeach
to cause people not to believe in the truthfulness of a witness in a lawsuit
The object of impeaching a witness is to discredit him and destroy, if possible, the force and effect of his testimony.
to charge an important person with a serious crime or misconduct; to formally charge a public official with a violation of the public trust
The Illinois House of Representatives earlier voted to impeach the governer over charges that he tried to "sell" Barack Obama's Senate seat.