Something that is not repeated or reproduced.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "one-off" in a sentence
"Fiscal discipline is theoretically a laudable goal, though in this case the agreement won't prevent governments from embarking on Keynesian spending sprees as "one-off and temporary measures"—the definition of "one-off" presumably being in the eye of the beholder."
"These so-called one-off expenses are not as uncommon as people think."
"The damning report said the violence could not be described as a "one-off" because of evidence that 1QLR troops abused and mistreated Iraqi civilians on other occasions."