What is Magistrate?

Legal Definition
The term magistrate is used in a variety of systems of governments and laws to refer to a civilian officer who administers the law. In ancient Rome, a magistratus was one of the highest ranking government officers, and possessed both judicial and executive powers. In other parts of the world, such as China, a magistrate was responsible for administration over a particular geographic area. Today, in some jurisdictions, a magistrate is a judicial officer who hears cases in a lower court, and typically deals with more minor or preliminary matters. In other jurisdictions (e.g., England and Wales), magistrates may be volunteers without formal legal training who perform a judicial role with regard to minor matters.
-- Wikipedia
Legal Definition
1. A local official whose authority is limited to whatever has been granted by statute or specified in the appointment.

2. In local or state courts, a justice of the peace or other judicial officer who has strictly limited authority and jurisdiction to hear certain cases, often criminal cases or small claims.

3. In U.S. federal courts, a judicial officer who has been appointed by a federal district judge to expedite the judicial process by conducting routine hearings and other proceedings.
Legal Definition
Mun. law. A public civil officer, invested with some part of the legislative, executive, or judicial power given by the constitution. In a narrower sense this term includes only inferior judicial officers, as justices of the peace.

2. The president of the United States is the chief magistrate of this nation; the governors are the chief magistrates of their respective states.

3. It is the duty of all magistrates to exercise the power, vested in them for the good of the people, according to law, and with zeal and fidelity. A neglect on the part of a magistrate to exercise the functions of his office, when required by law, is a misdemeanor. Vide 15 Vin. Ab. 144; Ayl. Pand. tit. 22; Dig. 30, 16, 57; Merl. Rep. h. t.; 13 Pick. R. 523
-- Bouviers Law Dictionary
Legal Definition
A public officer belonging to the civil organization of the state, and invested with powers and functions which may be either judicial, legislative or executive. But the term is commonly used in a narrower sense, designating, in England, a person entrusted with the commission of the peace, and, in America, one of the class of inferior judicial officers, such as justices of the peace and police justices. Martin v. State, 32 Ark. 124; Scanlan v. Wright, 13 Pick. (Mass.) 528, 25 Am. Dec. 344; Ex parte White, 15 Nev. 146, 37 Am. Rep. 466; Kurtz v. State, 22 Fla. 44, 1 Am. St. Rep. 173. A magistrate is an officer having power to issue a warrant for the arrest of a person charged with a public offence. Pen. Code Cal. § 807. The word "magistrate" does not necessarily imply an officer exercising any judicial functions, and might very well be held to embrace notaries and commissioners of deeds. Schultz v. Merchants' Ins. Co., 57 Mo. 336.
See also
-- Black's Law Dictionary
Legal Definition
A public officer clothed with some governmental power either by the constitution or the law; a justice of the peace; an inferior judge. See 30 Tex. App. 160, 28 Am. St. Rep. 899, 16 S. W. 903.
-- Ballentine's Law Dictionary