Do you believe in it? Does it have an explination?
If you don't know what it means then it's a theory that sometimes an absolute beginner can rush into a game and do well without any experience in it whatsoever.
I tend to get pretty extreme beginner's luck myself, to the point that if I've been on a losing streak in LoL then a sure fire way of winning the next one is insta-locking in a champion I've never played before and just building what I think may be good on them. And I easilly hold my own against some pretty good players.
For example my first game as Wukong about 2 weeks ago, I went jungle wukong and went legendary before 20 minutes. Then my success started to drop off in later games...