- inconceivable; unimaginable: the unthinkable size of the universe.
- not to be considered; out of the question: Such a suggestion is unthinkable.
- something that cannot be conceived or imagined, as something too unusual, vague, or disagreeable: Today's unthinkables are tomorrow's realities.
- not to be contemplated; out of the question
- unimaginable; inconceivable
- unreasonable; improbable
