piggybacking

The act of trying to get into a subway station without paying. The name originates from the method, in that someone will wait for another passenger to pay, and when the gates open, the other person will immediately walk in right behind them so the gates don't close immediately. This only works with fare gates that open and close automatically, and not turnstiles. The word is believed to have originated in Boston, where the act became more common after the MBTA increased fare prices.