Oath: A religious or solemn affirmation to tell the truth or to take a certain action. | Legal Definition of Oath

Obiter Dictum: Latin: an observation by a judge on a matter not specifically before the court or not necessary in determining the issue before the court. | Legal Definition of Obiter Dictum

Obligations: A legal requirement established by law, contract or as a result of unlawful harm caused to the person or property of another. | Legal Definition of Obligations

Obligee: The person who is to receive the benefit of someone else's obligation. | Legal Definition of Obligee

Obligor: A person who is contractually or legally, committed or obliged, to providing something to another person (the obligee). | Legal Definition of Obligor

Obscenity: A publication which is illegal because it is morally corruptive. | Legal Definition of Obscenity

Obstructing Justice: An act which tends to impede or thwart the administration of justice. | Legal Definition of Obstructing Justice

Occupational Rent: A matrimonial or joint tenant property compensatory claim based on an allegation that one spouse or joint tenant ought to be debited the value of her or his exclusive occupation of the family or jointly-held home. | Legal Definition of Occupational Rent

Occupational Therapy: The employment and function assessment and treatment of post-injury, illness or disability. | Legal Definition of Occupational Therapy

Occupiers' Liability: Liability of a person who controls land or building(s) in regards to damages caused to others who enter thereon. | Legal Definition of Occupiers' Liability

Offense: Conduct prohibited and punishable by the State. | Legal Definition of Offense

Offer: A explicit proposal to contract which, if accepted, completes the contract and binds both the person that made the offer and the person accepting the offer to the terms of the contract. | Legal Definition of Offer

Officer: A management-level employee of a corporation entrusted with discretion in the exercise of some portion of corporate powers. | Legal Definition of Officer

Officially Induced Error: A mistake of law caused by reliance upon erroneous legal advice obtained from an appropriate official. | Legal Definition of Officially Induced Error

Oligarchy: A form of government in which a few persons rule and govern by assuming all legislative and administrative authority. | Legal Definition of Oligarchy

Oligopoly: A market condition that results when there are but a few sellers | Legal Definition of Oligopoly

Ombudsman: A person whose occupation consists of investigating customer complaints against his or her employer. Many governments have ombudsmen who will investigate citizen complaints against government services. | Legal Definition of Ombudsman

Omnibus Bill: A draft law before a legislature which contains more than one substantive matter, or several minor matters which have been combined into one bill, ostensibly for the sake of convenience. | Legal Definition of Omnibus Bill

Onus: Latin: the burden. | Legal Definition of Onus

Open Fields Doctrine: There is no constitutionally protected expectation of privacy in open spaces. | Legal Definition of Open Fields Doctrine

Open Justice: A principle of the common law that proceedings ought to be open to the public, including the contents of court files and public viewing of trials. | Legal Definition of Open Justice

Open-Ended Agreement: A contract silent as to an essential term left either to the discretion of one of the contracting parties, or in making the duration of the contract indefinite. | Legal Definition of Open-Ended Agreement

Opening Statement: A lawyer or litigant's initial remarks at trial, to the finder of fact, either a judge or jury, setting out their road-map or case theory. | Legal Definition of Opening Statement

Opinio Juris: Latin: the sense of legal obligation. In international law, acceptance of a practice as sufficient to create legal obligations. | Legal Definition of Opinio Juris

Order: A formal written direction given by a member of the judiciary; a court decision without reasons. | Legal Definition of Order

Order of the Coif: The ancient order of barristers in England. | Legal Definition of Order of the Coif

Ordinance: An executive decision of a government which has not been subjected to a legislative assembly (contrary to a statute). | Legal Definition of Ordinance

Orphan: A person who has lost one or both of his or her natural parents. | Legal Definition of Orphan

Out-of-Court Settlement: An agreement between two litigants to settle a matter privately before the Court has rendered its decision. | Legal Definition of Out-of-Court Settlement

Overriding Error: A standard of appellate review, an error that must have altered the result or may well have altered the result. | Legal Definition of Overriding Error

Oversman: The Scottish law term for umpire. | Legal Definition of Oversman