v. 1) to declare under oath that one will tell the truth (sometimes "the truth, the whole truth and nothing but the truth"). Failure to tell the truth and do so knowingly is the crime of perjury. 2) to administer an oath to a witness that he/she will tell the truth, which is done by a notary public, a court clerk, a court reporter or anyone authorized by law to administer oaths. 3) to install into office by administering an oath. 4) to use profanity.