/ əˈstɒnɪʃɪŋ; NAmE əˈstɑːn-/ adjective
very surprising; difficult to believe
SYN amazing :
She ran 100m in an astonishing 10.9 seconds.
I find it absolutely astonishing that you didn't like it.
► as·ton·ish·ing·ly adverb :
Jack took the news astonishingly well.
Astonishingly, a crowd of several thousands turned out to hear him.