So implausible as to elicit disbelief: gave an incredible explanation of the cause of the accident. (adjective)
Astonishing: dressed with incredible speed. (adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "incredible" in a sentence
"Of the obstinate effort to bring about an armed intervention, on the lines marked out by Russells letter to Palmerston from Gotha, 17 September, 1862, nothing could be said beyond Gladstones plea in excuse for his speech in pursuance of the same effort, that it was the most singular and palpable error, the least excusable, a mistake of incredible grossness, which passed defence; but while Gladstone threw himself on the mercy of the public for his speech, he attempted no excuse for Lord Russell who led him into the incredible grossness of announcing the Foreign Secretarys intent."
"He asked them to lead a fundraising drive for Haiti, praising their efforts during past disasters and saying they can tap what he calls the incredible generosity and can-do spirit of the American people."
"But go over to the left, and you will see people who are happy with Colbert's what they call incredible roast, others blaming the mainstream media for not broadcasting more of what they say was a brave and shocking performance."