adverb
with a shiver; tremblingly
Describes a sudden shiver or chill running down the spine, often from fear, cold, or intense anticipation.
怖い話を聞いて、背中がぞくっとした。
Hearing the scary story, I felt a shiver run down my spine.
冷たい風が吹いて、ぞくっと身震いした。
A cold wind blew and I shivered.