Definition from Wiktionary, the free dictionary
unthinkable (not comparable)
- Incapable of being believed; incredible.
- Inconceivable or unimaginable; extremely improbable in a way that goes against common sense.
- Nothing is unthinkable, nothing impossible to the balanced person, provided it comes out of the needs of life and is dedicated to life's further development - Lewis Mumford
2011 October 23, Tom Fordyce, “2011 Rugby World Cup final: New Zealand 8-7 France”, BBC Sport:
- With 16 minutes left on the clock and the tension climbing through the roof, Trinh-Duc tried his luck with a penalty from just inside halfway only to push it wide, but the unthinkable now seemed a real possibility.
incapable of being believed; incredible
inconceivable or unimaginable; extremely improbable in a way that goes against common sense
- “unthinkable” in Douglas Harper, Online Etymology Dictionary (2001).