싱글벙글 (sing-geul-beong-geul) – all smiles
You would typically use 싱글벙글 with 웃다 so that it places emphasis that the person (subject) is extremely happy.
아저시는 복권 당첨되서 돈을 벌고 은행으로 싱글벙글 웃었어.
The uncle struck lottery and went to the bank all smiles after taking the money.
나 시험을 잘 보니 집으로 싱글벙글 웃고 엄마한테 말했어.
I did well for my test so I went home all smiles and told Mom about it.