To drive too closely behind another vehicle, or to follow someone very closely; also means to have a party in a parking lot before a game or event.
Combination of 'tail' (to follow) and 'gate' (the hinged door at the back of a truck). The verb meaning developed from the physical gate being at the tail of a vehicle.
Tailgating at sports events started because trucks had those convenient gates you could open and sit on—what began as a practical spot to sit became America's favorite pre-game party tradition!
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