un-think-able (an adjective of 15th century origin)
1. incapable of being conceived, considered, or imagined.
2. not reasonable, plausible, or probable.
An example of its use in a sentence:
The other night, the "unthinkable" happened...
How Could THIS Happen? - Rachel on LGPedia.
RedEarth88 on LGPedia.
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