Old American slang: to leave very quickly, usually escaping something — 'he lit out for the hills'. Honestly, you will meet this in old books and cowboy stories, not in conversation; it is at the end of Huckleberry Finn ('light out for the Territory'). I include it so the book does not confuse you, not so you use it. Past tense is 'lit out'. No object; often 'light out for' a place.