To fail to meet an obligation.
If you do not make your payments, you will default on your loan.
To lose a competition by failing to compete.
If you refuse to wear a proper uniform, you will not be allowed to compete and will default this match.
To assume a value when none was given; to presume a tentative value or standard.
If you don't specify a number of items, it defaults to 1.
To fail to appear and answer a summons and complaint.
The act or result of being defaulted, especially a failure to meet a financial obligation.