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Ultra Vires

Latin for "beyond the life", i.e., outside authority. This phrase is most often used to describe the unauthorized act of a corporate officer or trustee who undertakes to do an act that is beyond his actual power.

Unclean Hands

The doctrine of "unclean hands" applies to cases where one party seeks to persuade the court to exercise its equitable discretion, so the court looks to see if either party has dirty hands, e.g., whether one party has done something unfair with regard to the issues of the case. It is not enough if one party has an unsavory history. The "unclean hands" must apply to the issues in controversy, such as preventing the other party from performing his contract, etc. The ancient maxim is, "He who comes to equity must come with clean hands."

Undue Influence

When someone influences another who is susceptible of being swayed in opinion or decision because of mental infirmity or other debilitating factors, causing the weakened person to make a legal choice (such as changing their will) the wrongful act is called undue influence.

Upon being presented with sufficient evidence of undue influence, a court my reverse the act, e.g., nullifying the will.

In some states a legal presumption of undue influence arises if the influencer occupies a position of trust with the person unduly influenced (e.g., a child or long-term caretaker), actively participates in the influenced act (e.g., taking the person of weakened mind to a lawyer to change the will), and is favored by the influenced act (e.g., becoming a beneficiary under the altered will).

Unintentional

Without intent. Under some concepts of common law, every crime requires the element of intent, i.e., the act complained of must result from some intentional act of the accused. In civil law, this is not always so, since a civil action will lie for damages resulting from bone-headed stupidity or blind ignorance as well as for damages resulting from the defendant’s direct intention to cause the plaintiff injury.

Unjust Enrichment

A cause of action in equity to prevent one party from gaining an unfair advantage (unjust enrichment) at the expense of another party without some reasonable benefit being returned.

This may be called the "something for nothing" doctrine. Equity rules the law. Therefore, where one party is unjustly enriched by an act the deprives another of property (even if the act is technically "legal") American courts can exercise their equitable power to reverse the gain to prevent unjust enrichment, because equity rules the law.

This is sometimes a difficult concept for novices in the law to understand. Some believe they can make a wrong "right" if they find a "law" to hide in. Though this was clearly the way things were in the days of Charles Dickens (read Dickens’ Bleak House and Hard Times to learn the pitiable state of the legal system in England only two hundred years ago, when the poor were without any hope at all before the pomp of courts where white-powdered wigs strutted about the courtrooms spouting every excuse under heaven why wrong should be treated as right.), our American legal system today will not tolerate such injustices (if the wronged party knows what his lawyer should be doing to recover the loss and presses forward with clean hands).

Equity uncovers the cloak of unjust men and works "right" to prevent wrong, even where there is "law" that would otherwise give the unjust person the advantage.

An example of  unjust enrichment is where a landlord enters into a lease with his tenant who later is unable to pay the rent as it comes due and must vacate the premises before the expiration of his lease. Certainly, under most jurisdictions in America, the landlord is entitled to his rent money, even after the tenant moves out, because there is remaining time agreed to under the lease, and the tenant promised to pay for the full term of the lease. Otherwise the landlord is left with empty property, and the tenant is unjustly enriched by being let off the hook. The landlord should be permitted to sue and get an un-paid rent judgment against the tenant for the remainder of the lease term ... if, in fact, he is unable to rent the property to someone else. But, suppose the landlord were to find another tenant and start collecting rent from the new tenant while suing the old tenant. This would be a form of unjust enrichment, and equity would prevent the landlord from double-dipping.

There are many other examples of unjust enrichment, some of which seem to fly in the face of ancient contract principles. For example, if a young man entrusts the care of his farm to a friend while he goes off to war and returns years later to discover his friend has claimed title to the land by adverse possession, the court could exercise its equitable powers to hear an action brought for unjust enrichment against the friend to prevent the wrong.

Remember: Equity rules the law. 

Usurious

Of or related to usury, q.v.

Usury

The act of charging exorbitant rates of interest. In some states usury laws render promissory notes or other obligations exacting exorbitant interest rates unenforceable in court. In some circumstances, usury is a punishable crime related to fraud.

Ux

See uxor.

Uxor

Strictly a lawfully married wife. The term is sometimes shortened to simply "ux".