Dumbfounded
Taken Aback, Astonished
noun
あっけ
仰天 (ぎょうてん) Taken Aback, Amazed, Horrified, Flabbergasted
呆気 (あっけ) Dumbfounded, Taken Aback, Astonished
呆け (ぼけ) Idiot, Fool
He was so Dumbfounded his head started to ache あっけ