What is Certiorari?

CERTIORARI  defined:

When any tribunal, board, or officer exercising judicial functions has acted without or in excess of its or his jurisdiction, or with grave abuse of discretion, and there is no appeal, nor any plain, speedy, and adequate remedy in the ordinary course of law, a person aggrieved thereby may file a verified petition for certiorari in the proper court alleging the facts with certainty and praying that judgment be rendered annulling or modifying the proceedings, as the law requires, of such tribunal, board or officer.

**Definition taken from Justice Isagani Cruz (Constitutional Law, 2003)