adverb, noun or participle which takes 'suru'
startled; taken aback
Mimetic word describing a sudden, sharp surprise or fright, often in reaction to something unexpected or shocking.
突然の大きな音にぎょっとした。
I was startled by the sudden loud noise.
彼の変わりようにぎょっとし
I was taken aback by how much he had changed.