喷 (pēn) = 'to spurt / spew,' 饭 (fàn) = 'rice/food.' Picture someone literally spraying their lunch across the table laughing — that's the image. Often paired with 令人 or 让人: 令人喷饭 = 'enough to make you spit out your food.'
register
Colloquial and a touch dramatic. Online you'll see 笑喷 with the same vibe. The classical phrase 喷饭满案 ('spew rice all over the table') traces back to Su Shi's writings.
