What is Assassination?

Legal Definition
Assassination is the murder of a prominent person, often a political leader or ruler, usually for political reasons or payment.

An assassination may be prompted by religious, political, or military motives; it is an act that may be done for financial gain, to avenge a grievance, from a desire to acquire fame or notoriety, or because of a military, security or insurgent group's command to carry out the homicide.
-- Wikipedia
Legal Definition
Crim. law. A murder committed by an assassin. By assassination is understood a murder committed for hire in money, without any provocation or cause of resentment given by the person against whom the crime is directed. Ersk. Inst. B. 4, t. 4, n. 45.
-- Bouviers Law Dictionary
Legal Definition
Murder committed for hire, without provocation or cause of resentment given to the murderer by the person upon whom the crime is committed. Ersk. Inst. 4, 4, 45. A murder committed treacherously, or by stealth or surprise, or by lying in wait.
-- Black's Law Dictionary
Legal Definition
Murder done for hire alone.
-- Ballentine's Law Dictionary