IPA: /ˈæɡəˌnaɪzɪŋli/
KK: /ˈæɡənˌaɪzɪŋli/
In a way that causes great pain or suffering.
She waited agonizingly for the results of her exam.
Agonizingly → It is formed from "agonize" (from Greek "agonizesthai", meaning to struggle or contend) and the suffix "-ly" (meaning in a manner of). The word "agonizingly" describes something done in a manner that involves great struggle or suffering.
Think of the word 'agonize' which means to struggle or suffer, and remember that 'agonizingly' describes doing something in a way that involves great pain or distress.