non·per·for·mance /ˌnän-pər-'fȯr-məns/ n: neglect or failure to perform
Merriam-Webster’s Dictionary of Law. Merriam-Webster. 1996.
avoidance, breach of promise, default, delinquency, dereliction of duty, disregard, dutilessness, evasion, evasion of duty, failure to perform, idleness, inactivity, inexecution, laxity, neglect, negligence, noncompletion, noncompliance, noncooperation, nonfeasance, nonfulfillment, nonpractice, omission, truancy, unduteousness, undutifulness, unfulfillment
associated concepts: nonperformance of a contract, nonperformance of a duty
breach, default, deficiency, delinquency (failure of duty), dereliction, failure (falling short), frustration, laches, laxity, miscarriage, neglect, nonfeasance
Burton's Legal Thesaurus. William C. Burton. 2006
n.Failure to perform some duty or obligation; failure to perform according to the terms of a contract.
The Essential Law Dictionary. — Sphinx Publishing, An imprint of Sourcebooks, Inc. Amy Hackney Blackwell. 2008.