What exactly is a big stack

[BigChris407]

Without any specific reads but feeling comfortable that you can play well against the other players at the table, what is a safe amount of BB lets say to start splashing around. Playing more aggressive then you would if you where average. I'm talking mostly during the large body of the tournament, not close to the bubble or at final table. I would think on the button starting req. for raise would be little looser because everyone would be playing pretty tight. Thoughts??