imo, flirting is the art of seduction, but draw the line of limitation, for example, you have a gf or a wife, you went to a bar, boys night out, you spotted a chick, you exchange smile,toast, maybe dance together, but no kissing nor any (more)intimate connection, you dont exchange numbers and most importantly you dont think of her the day after...

cheating is you hide start to hide things from your gf or wife to establish a self gratification...