polite: 잘 먹었어요 · casual: 잘 먹었어
thank you for the meal (said after eating)
Example
할머니, 정말 맛있게 잘 먹었습니다.
Grandma, thank you — that was really delicious.
Word parts
Literally 'I ate well' — the past-tense partner of 잘 먹겠습니다, said after the meal.
Good to know
Said after eating to the host or the person who paid — also to restaurant staff when leaving.