unbelievably
adv. degree B2 Upper Intermediate US //ˌənbəˈɫivəbɫi// UK //ʌnbɪlˈiːvəbli// un·be·liev·ably
adv. in a way that is very hard to believe because it is so extreme. You use it to emphasize how good, bad, or surprising something is.
adv. to an extent that is improbable or difficult to credit. Often functions as an intensifier to modify adjectives or other adverbs.
The food at that new restaurant was unbelievably good.
The team managed to finish the entire project unbelievably quickly, despite having only two days to work.
The mountain range looked unbelievably beautiful as the setting sun cast a deep purple glow over the snow-capped peaks.
Usage
Degree adverb — typically placed immediately before the adjective or adverb it modifies.