Her new haircut was strikingly different from before and caught everyone's attention.

strikingly 是形容词 striking 的副词形式，striking 来自动词 strike（打击、打动），引申为"引人注目的、显著的"。 strikingly 作为副词，意思是"显著地、引人注目地"，用来强调程度非常明显。