Strictly speaking, a default occurs when a borrower has broken the terms of a loan or other debt, for example if a borrower misses a payment. The term is also loosely used to mean any situation that makes clear that a borrower can no longer repay its debts in full, such as bankruptcy or a debt restructuring.
A default can have a number of important implications. If a borrower is in default on any one debt, then all of its lenders may be able to demand that the borrower immediately repay them. Lenders may also be required to write off their losses on the loans they have made.