Indescribable means too extreme to be put into words. The writer gives up, deliberately.
It is used for joy, horror, smells and pain, and it is a rhetorical move as much as a description, since claiming something cannot be described is a way of insisting on its scale. Careful writing uses it sparingly, on the grounds that describing things is the job. It works with both good and bad extremes. The adverb indescribably usually props up an adjective, as in indescribably awful.
1adjectiveindescribableToo extreme or unusual to be described in words.
“The relief was indescribable.”
Proto-Indo-European
*(s)kreybʰ-
Latin
dēscrībō — to copy off, transcribe, sketch off, describe in painting or writing
Old French
descrivre
Middle English
descriven
English
describe
English, today
indescribable
Built from
From in + describe + able. describe comes from Middle English descriven, from Old French descrivre, from Latin dēscrībō (“to copy off, transcribe, sketch off, describe in painting or writing”), from dē (“off”) + scrībō (“write”); see scribe and shrive. Displaced native āmearcian.
Etymology from Wiktionary, CC BY-SA