1) Failure to file an answer or other response to a summons or complaint in a lawsuit. After a certain period has passed, the plaintiff may ask the court for a default judgment, which means the defendant who failed to respond loses the case. A defendant who has a legally sufficient reason for failing to respond (for example, the defendant never received the summons) may file a motion asking the court to overturn the default judgment and allow the defendant to defend the lawsuit. 2) Failure to pay a debt or meet other obligations of a loan agreement. For example, a debtor may default on a car loan by failing to make required monthly payments or by failing to carry adequate insurance as required by the loan agreement.