I think I will be more liberal with my answer than just talking about when I was actually on fire. no matter how much comedic potential it has. The definition that some people use is having a fire, or passion for things. I think the most on "fire" I was ever "on" was when I was spreading the knowledge and the truth that I had found in God. Everything seemed to click around me and in describable accordance with God in my actions. It was a way that some would describe as being at one with the universe, or knowing the Tao, a sixth stage to Nirvana. I had chosen the path to be through a non-secular Christian group. I suddenly had this ability to speak to people unlike ever before. I'm not particularly convincing, other times I stutter or slur my speech, but when I was on fire for God I was unstoppable. I went from zero to hero fast. I won't bored you with anymore right now.