Definition of "indescribably"

The appearance of the dead was indescribably ghastly.

1879, John McElroy, chapter 24, in Andersonville: A Story of Rebel Military Prisons

There was something indescribably nerve-shaking and menacing in that constant mutter, which seemed to shape itself into the very syllables of the half-breed, endlessly repeated, "We will kill you if we can."

1912, Arthur Conan Doyle, The Lost World […], London, New York, N.Y.: Hodder and Stoughton

“I felt this sense of relief that I didn’t have to lie anymore, and that I could start taking responsibility even though I felt indescribably bad.”

2023 October 11, David Yaffe-Bellany, Matthew Goldstein, J. Edward Moreno, quoting Caroline Ellison, “Caroline Ellison Says She and Sam Bankman-Fried Lied for Years”, in The New York Times‎