> They mean consistently make better decisions than a baseline index investor in a way that isn't luck.
How would you know it is or is not luck?
> roulette
Has no winning strategy - it's very different.
The winning strategy with stocks is understanding the underlying businesses better than the average investor. Peter Lynch's Magellan fund did consistently better than others because Lynch had insights others didn't. When others figured it out, Magellan's returns retreated to market levels.
I.e. investors can do better than average if they have insight others don't have and stay below the radar.