ROFL is internet shorthand for rolling on the floor laughing. You type it when something is so funny you want to say you are not just smiling — you have, in pretend, fallen over. It is casual chat language, and by now a little old-fashioned: people who grew up with early chat rooms still use it; many younger people just send 😂. You will see it in comments, messages, and old memes, not in school essays or work email. Some people say the letters one by one; some say it like “roffle”. Stronger, ruder cousins exist; those do not belong in polite writing.

ROFL（網路用語：笑到在地上打滾；比 LOL 更誇張，現在年輕人較多用表情符號）