1. The vehicle in which you find yourself when you ROFL.
2. A state of mind that you obtain when you ROFL.
3. The funniest thing John's ever heard.
Guy #1: "So today I was just standing there and then BAM! I crapped my pants!"
Guy #2: "Rofflcopter!"
Something so amusing, or indeed so ROFL, it causes one to spin.
Napalm in the morning makes me rofflcopter