Definition of rush
We'll talk about rush when, on several hands, you have very good hands. Imagine that in rush hands, you have 2 times AA preflop, 1 time KK preflop, that you hit a flop 7-7-8 with 78 in hand and that you hit a flop 9-A-9 with A9 in hand. You will probably win all the pots and then it will be said that you are on a rush. A rush is doubly profitable. Why double? On the one hand, you have great hands so you'll be favorites to win the jackpot. Two, because if your opponents see you playing almost all hands in a row, after a few hands they will think you are overreacting or in a tilt. So they'll start with you caller light.
The rush of cards when no one sees your cards
Sometimes you will be in a rush of cards and no one will see your cards. For example, you go in an 4 bet preflop and your opponent goes down. Then you bet flop in another pot and your opponent folds again. If this is the case, since no one has seen your cards, players might start to suspect you are bluffing. If you are still in a rush the next hands, feel free to go to overbet with your very strong hands; your flop folding will be greatly reduced.