In legal terminology, default refers to a failure to fulfill a legal obligation or duty. For example, a default by a borrower under a loan agreement permits a lender to take certain actions in response to the default.
Default is often used to refer to the non-appearance of the defendant within the time prescribed by law to defend himself. It also signifies the non-appearance of the plaintiff to prosecute his claim. In such cases, a judgment will be rendered in favor of the non-defaulting party automatically, which is called a "default judgment".