General Synonym:
* Failure
In the context of a loan or payment:
* Nonpayment
* Missed payment
* Delinquency
In the context of a computer or software:
* Standard
* Preset
* Predefined
In the context of a choice:
* Automatic
* Predetermined
* Standard setting
In the context of a legal term:
* Breach
* Violation
More specific synonyms:
* Omission
* Neglect
* Forfeiture
* Lapse
* Fallback
* Setback
* Failure to perform
To choose the best synonym, consider the specific meaning of "default" in the sentence.