Inconceivable (adjective)

1. Impossible to imagine or comprehend; beyond understanding.
2. Not able to be believed or accepted as true; incredible.
3. Not able to be thought of as happening or existing.

Origin:

From the latin word "inconcepibilis" meaning "impossible to imagine".

Examples:

1. It was inconceivable that he would win the election.
2. It was inconceivable that the company would go bankrupt.
3. The idea of time travel is still inconceivable.
4. The scale of the disaster was inconceivable.
5. The amount of money he asked for was inconceivable.