1. So implausible as to elicit disbelief; unbelievable: gave an incredible explanation of the cause of the accident.
2. Astonishing, extraordinary, or extreme: dressed with incredible speed.
[Middle English, from Latin incrēdibilis : in-, not; see IN-1 + crēdibilis, believable; see CREDIBLE.]
in·cred′i·bili·ty, in·credi·ble·ness n.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.