Guardian

A person who has legal responsibility of the property and the person of one who is unable to manage his or her own matters, for example, a child or mentally-disabled person. Custody is given by legal appointment or by the effect of a written law.

Additional Sources

Answers.com

One who is legally responsible for the care and management of the person or property of an incompetent or a minor.

Duhaime Legal Dictionary

An individual who, by written or Court appointment or by the effect of a statute, is given custody of both or either of the property or the person of one who is unable to manage their own affairs, such as a child or a mentally-disabled person.

American practise is to use the full term "legal guardian" whereas other common law jurisdictions use either guardian or custodians.

Most jurisdictions allow parents to specify, in a will or will-like document, a third-party to become the legal guardian of their children should both parents die before the child(ren) attain the age of majority, subject always to the jurisdiction of the Court to vary the designation if it is appropriate.

A legal guardian exercises most of the legal rights of the person for whom they are legal guardian, until they either reach the age of majority or, in the case of legal guardianship of an incompetent adult, otherwise retrieve their capacity to manage their own affairs.

FindLaw

One who has or is entitled or legally appointed to the care and management of the person or property of another.

Law.com Dictionary

n. a person who has been appointed by a judge to take care of a minor child or incompetent adult (both called "ward") personally and/or manage that person's affairs. To become a guardian of a child either the party intending to be the guardian or another family member, a close friend or a local official responsible for a minor's welfare will petition the court to appoint the guardian. In the case of a minor, the guardianship remains under court supervision until the child reaches majority at 18. Naming someone in a will as guardian of one's child in case of the death of the parent is merely a nomination. The judge does not have to honor that request, although he/she usually does. Sadly, often a parent must petition to become the guardian of his/her child's "estate" if the child inherits or receives a gift of substantial assets, including the situation in which a parent gives his/her own child an interest in real property or stocks. Therefore, that type of gift should be avoided and a trust created instead. While the term "guardian" may refer to someone who is appointed to care for and/or handle the affairs of a person who is incompetent or incapable of administering his/her affairs, this is more often called a "conservator" under a conservatorship.

Lect Law Library

A person or institution named in a will or a temporary guardianship who is responsible for the care of minor children. (2) Person assigned by the court to take care of minor children or incompetent adults. Sometimes called a conservator.

Wikipedia

A legal guardian a person who has the legal authority (and the corresponding duty) to care for the personal and property interests of another person, called a ward. Usually, a person has the status of guardian because the ward is incapable of caring for his or her own interests due to infancy, incapacity, or disability. Most countries and states have laws that provide that the parents of a minor child are the legal guardians of that child, and that the parents can designate who shall become the child's legal guardian in the event of death.

Courts generally have the power to appoint a guardian for an individual in need of special protection. A guardian with responsibility for both the personal well-being and the financial interests of the ward is a general guardian. A person may also be appointed as a special guardian, having limited powers over the interests of the ward. A special guardian may, for example, be given the legal right to determine the disposition of the ward's property without being given any authority over the ward's person. A guardian appointed to represent the interests of a person with respect to a single action in litigation is a guardian ad litem.

Some jurisdictions allow a parent of a child to exercise the authority of a legal guardian without a formal court appointment. In such circumstances the parent acting in that capacity is called the natural guardian of that parent's child.