unthinkable

adj

1. That cannot be believed.

   “Near-synonyms: unbelievable, incredible, inconceivable”

2. Inconceivable or unimaginable; extremely improbable in a way that goes against common sense.

   “Near-synonyms: inconceivable, imponderable”

   “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”

   “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.”

   “The ruling also comes amid calls from an opposition party for a review of the royal insult law, which would have been unthinkable just a few years ago.”

   “It reopened as St Pancras Renaissance Hotel London in the early part of this century, and it now seens unthinkable to demolish such a structure.”

3. Extremely improper; extremely at odds with norms of expected behavior.

   “Near-synonyms: taboo, unspeakable, unutterable, inconceivable”

   “I want you to know that P.A.C. will pay for a child psychiatrist to come in and testify on behalf of the child so that the homosexual father will not be able to have that little girl overnight and weekends to expose her to what is unthinkable.”

noun

1. Something, or various things collectively, that one dare not think about, dare not do, or dare not think about doing.

   “Near-synonym: unspeakable”

   “do the unthinkable”

   “did the unthinkable”