1. What does it mean?
뿜다 ordinarily means to spurt or spray something out. In casual reactions, 뿜었다 can describe laughter bursting out unexpectedly, sometimes with the image of nearly spraying a drink at a joke.
Also written or said as 뿜었다, ppumda
2. The nuance
Context matters: 물을 뿜다 can mean literally spraying water, while 댓글 보고 뿜었다 usually reports amusement. It is more sudden and physical-sounding than a routine ㅋㅋ.
3. Examples
“진지한 안내문 끝에 붙은 농담 보고 뿜었어.”
The joke at the end of the serious notice made me burst out laughing.
“물 마시다가 네 표정 보고 뿜을 뻔했잖아.”
Your expression nearly made me spit out my water laughing.
Sources
References support the meaning and usage. Example sentences are written for NoCapWiki.