황송해요 · 황송했어요 · 황송한 (+noun)
to be humbled, overwhelmed with gratitude (by undeserved kindness)
Example
이렇게 귀한 선물을 주시니 황송합니다.
I'm truly humbled that you would give me such a precious gift.
Word parts
황 fearful+송 fearful
Literally 'awed and fearful' — overwhelmed by a superior's kindness.
Good to know
Used toward elders or superiors; 황송하다 mixes gratitude with feeling unworthy.