In criminal law. The willful assertion as to a matter of fact, opinion, belief, or knowledge, made by a witness in a judicial proceeding as part of his evidence, either upon oath or in any form allowed by law to be substituted for an oath, whether such evidence is given in open court, or in an affidavit, or otherwise, such assertion being known to such witness to be false, and being intended by him to mislead the court, jury, or person holding the proceeding. 2 Whart. Crim. Law.