1) failure to make Mortgage payments on a timely basis or to comply with other requirements of a Mortgage. 2) the nonperformance of a duty or obligation that is part of a contract. the most common occurrence of default on the part of a buyer or lessee is nonpayment of money when due. a default is normally a breach of contract, and the nondefaulting party can seek legal remedies to recover any loss. defaults in long-term leases or contracts for deed other than nonpayment might be failure to pay real estate taxes, damage to the property and so forth.