To drive too closely behind another vehicle.
This can be dangerous and make people feel nervous or annoyed.
Examples:
He tailgated the car in front of him.
She doesn't like it when people tailgate her.
The police stopped him for tailgating.
The big truck tailgated the small car and made the driver mad.
He always tailgates and never leaves enough space.
She got a ticket for tailgating too much.