INDESCRIBABLY
ineffably, indescribably, unutterably, unspeakably, inexpressibly
(adverb) to an inexpressible degree; “she was looking very young tonight, and, as usual, indescribably beautiful, in a simple strapless dress of a green and white silky cotton”
Source: WordNet® 3.1
Etymology
Adverb
indescribably (comparative more indescribably, superlative most indescribably)
In an indescribable manner.
Source: Wiktionary
INDESCRIBABLE
In`de*scrib"a*ble, a.
Definition: Incapable of being described.
– In`de*scrib"a*bly, adv.
Source: Webster’s Unabridged Dictionary 1913 Edition