Definition of "unthinkable" []

• Impossible to imagine; inconceivable: an unthinkable amount of money. (adjective)
• Contrary to what is plausible or probable: That this project would achieve ultimate success was unthinkable at the time. (adjective)
• Not to be thought of or considered; out of the question: Raising taxes was politically unthinkable. (adjective)

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.

• "The courage to face the unthinkable is at the core of this magnificent new novel."
• "The one option you need to regard as unthinkable is to stay with this person."
• "The unthinkable is the collapse of the banking system."