wondrously; marvellously; uncannily; like a charm
Expresses that something happens or works in a way that feels almost magical, surprisingly effective, or beyond ordinary explanation. Often used adverbially to modify verbs or whole clauses.
After taking this medicine, the pain disappeared as if by magic.
His explanation was marvellously easy to understand.
A fixed expression combining 不思議 (mysterious, wondrous) with な (attributive form of the copula) and ほど (degree, extent). The exact historical derivation is uncertain, but it functions as a set adverbial phrase.