IPA: /ˈtʃɪl.ɪŋ.li/
KK: /ˈtʃɪlɪŋli/
In a way that causes fear or discomfort; in a frightening manner.
The movie ended with a chillingly realistic scene that left the audience in shock.
Chillingly → It is formed from "chill" (from Old English *ciele*, meaning cold) and "-ingly" (a suffix used to form adverbs indicating manner). The word "chillingly" means in a manner that causes a feeling of coldness or fear.
Think of something that makes you feel 'cold' ('chill') and how it can happen 'in a manner' ('-ingly') that is unsettling or frightening.