Green’s Dictionary of Slang

1. to drive a car closely (too closely) behind the one in front; thus tailgating n.

1955		M.W. Frazier ‘Truck Drivers’ Language’ in AS XXX:2 94: TAILGATING, ger. Driving too closely behind the vehicle ahead.
1978		P. Theroux Picture Palace 44: In the car, tailgating some retired gent.
1983		S. King Christine 58: I goosed the accelerator again, and this time I almost tailgated Arnie.
1996		P. Cornwell Cause of Death (1997) 274: This person’s been tailgating me for the better part of the day.
2001		Enniscorthy Guardian 13 June 51/1: Tailgating is the biggest single cause of road rage.
2006		Irish Indep. 15 Nov. 26/2: [headline] Tailgating impossible to avoid on the motorway.
2023		(con. 1962) J. Ellroy Enchanters 38: She hopped lanes and tailgated.

2. also in fig. use, to follow, esp. of things that are endlessly repetitive.

1977		Times Lit. Supp. 20 May 618/3: Pictures tailgate each other, wall to wall, and floor to ceiling, in the authentic eighteenth-century manner .
1997		N. Barlay Curvy Lovebox 111: The three Shitskys are behind him tailgatin’ right up his ass.

3. (US campus) to watch women passing by.

2000

M. Collins Keepers of Truth 75: Driving onto campuses [...] in his fancy car, tailgating and picking up women.

4. (US und.) to steal from the back of a truck.

2000

Lehr & O’Neill Black Mass 25: Whitey Bulger was already tailgating merchandise off the back of delivery trucks in Boston’s minority neighborhoods.