What is Imprisonment?

Legal Definition
Imprisonment (from imprison Old French, French emprisonner, from en in + prison prison, from Latin prensio, arrest, from prehendere, prendere, to seize) is the restraint of a person's liberty, for any cause whatsoever, whether by authority of the government, or by a person acting without such authority. In the latter case it is "false imprisonment". Imprisonment does not necessarily imply a place of confinement, with bolts and bars, but may be exercised by any use or display of force, lawfully or unlawfully, wherever displayed, even in the open street. People become prisoners, wherever they may be, by the mere word or touch of a duly authorized officer directed to that end. Usually, however, imprisonment is understood to imply an actual confinement in a jail or prison employed for the purpose according to the provisions of law.
-- Wikipedia
Legal Definition
The restraint of a person contrary to his will. 2 Inst. 589; Baldw. Rep. 239, 600. Imprisonment is either lawful or unlawful; lawful imprisonment is used either for crimes or for the appearance of a party in a civil suit, or on arrest in execution.

2. Imprisonment for crimes is either for the appearance of a person accused, as when he cannot give bail; or it is the effect of a sentence, and then it is a part of the punishnient.

3. Imprisonment in civil cases takes place when a defendant on being sued on bailable process refuses or cannot give the bail legally demanded, or is under a capias ad satisfaciendum, when he is taken in execution under a judgment. An unlawful imprisonment, commonly called false imprisonment, (q. v.) meaus any illegal imprisonment whatever, either with or without process, or under color of process wholly illegal, without regard to any question whether any crime has been committed or a debt due.

4. As to what will amount to an imprisonment, the most obvious modes are confinement in a prison or a private house, but a forcible detention in the street, or the touching of a person by a peace officer by way of arrest, are also imprisonments. Bac. Ab. Trespass, D 3; 1 Esp. R. 431, 526. It has been decided that lifting up a person in his chair, and carrying him out of the room in which he was sitting with others, and excluding him from the room, was not an imprisonment; 1 Chit. Pr. 48; and the merely giving charge of a person to a peace officer, not followed by any actual apprehension of the person, does not amount to an imprisonment, though the party to avoid it, next day attend at a police; 1 Esp. R. 431; New Rep. 211; 1 Carr. & Pavn. 153; S. C. II Eng. Com. Law, R. 351; and if, in consequence of a message from a sheriff's officer holding a writ, the defendant execute and send him a bail bond, such submission to the process will not constitute an arrest. 6 Bar. & Cres. 528; S. C. 13 Eng. Com. Law Rep. 245; Dowl. & R. 233. Vide, generally, 14 Vin. Ab. 342; 4 Com. Dig. 618; 1 Chit. Pr. 47; Merl. R¬ępert. mot Emprisonment; 17 Eng. Com. L. R. 246, n.
-- Bouviers Law Dictionary
Legal Definition
The act of putting or cenfining a man in prison; the restraint of a man's personal liberty; coercion exercised upon a person to prevent the free exercise of his powers of locomotion. State v. Shaw, 73 Vt. 149, 50 Atl. 863; In re Langs-low, 167 N. Y. 314, 60 N. E. 590; In re Langan (C. Ct) 123 Fed. 134; Steere v. Field, 22 Fed. Cas. 1221. It is not a necessary part of the definition that the confinement should be in a place usually appropriated to that purpose; it may be in a locality used only for the specific occasion; or it may take place without the actual application of any physical agencies of restraint, (such as locks or bars,) but by verbal compulsion and the display of available force. See Pike v. Hanson, 9 N. H. 491. Any forcible detention of a man's person, or control over his movements, is imprisonment. Lawson v. Buzines, 3 Har. (Del.) 416. See False imprisonment.
-- Black's Law Dictionary
Legal Definition
Every confinement of the person, whether in a prison, a house or on the street. See 12 Ark. 43, 54 Am. Dec. 250.
-- Ballentine's Law Dictionary