Definitions
1.NounA writ (“written order”) requiring someone to appear in court, or at a deposition or some other legal proceeding, as a witness to give testimony (a subpoena ad testificandum) or to produce evidence (subpoena duces tecum), in default of which the person may be punished.
2.NounA writ requiring a defendant to appear in court to answer a plaintiff's claim (a subpoena ad respondendum); in England and Wales, and Ireland, this writ was formerly issued by the Court of Chancery at the plaintiff's request to commence a suit, but the procedure was abolished in 1852.
3.NounA motive or thing which can compel or demand something, or summon someone.
4.VerbTo summon (someone) with a subpoena (noun sense 1) to appear in court, or at a deposition or some other legal proceeding, as a witness to give testimony or to produce evidence; to serve a subpoena on (someone).
5.VerbTo require (a document or other evidence) to be produced before a court, or at a deposition or some other legal proceeding.
6.VerbTo compel or summon (someone or something); to demand.