[1] anything goes; as one pleases; not confirming to rules; casually; randomly. | Std. Chin.: 隨便
[2] a fairly common term for 豉油煎蛋飯 (due to it being nearly homophonous to 豉蛋), which many kids love to eat in HK, and often as a joke for people who reply to "what do you want to eat" with "是但" and the comeback being 豉油煎蛋飯呀? (could mean "are you still a kid"? or "are you that cheap"? because it's just soy sauce and a fried egg on rice)