Incredulous (adjective)

1. Unwilling to believe, skeptical.
2. Unable to believe something.
3. Showing disbelief or doubt.

Origin:

From latin incredulus, from in- ("not") + credulus ("credulous").

Examples:

1. He looked at her in an incredulous way when she told him the news.
2. I was incredulous when I heard the story.
3. The audience was incredulous when the magician made the elephant disappear.
4. She was incredulous at the idea of winning the lottery.
5. He was incredulous at the thought of the company going bankrupt.