litigate
To take a disagreement to court to be decided.
To litigate means to take a disagreement to court and settle it through the legal system. When people or organizations litigate, they hire lawyers and present their case to a judge or jury, who decides who's right according to the law.
Imagine two neighbors disagree about where the property line runs between their yards. They might try talking it out first, but if they can't agree, one might decide to litigate the dispute. That means filing a lawsuit and letting a court make the final decision. Companies also litigate when they have serious disagreements: a toy company might litigate if another company copies their invention, or two businesses might litigate over a broken contract.
When lawyers handle such cases, they're said to practice litigation. A case currently being argued in court is said to be in litigation.
Litigation takes time and costs money, so most people try to work out their problems through discussion or negotiation first. But sometimes, when stakes are high or disagreements run deep, litigation becomes necessary to get a fair, legally binding answer. The court system exists partly for this purpose: to resolve conflicts when people can't resolve them on their own.