noun

• (automotive) A hinged board or hatch at the rear of a vehicle that can be lowered for loading and unloading.
  "When they first attached tailgates to cars, we were hooked. By the 1970s, wagons with names like Vista Cruiser and Town & Country sported tailgates as big as dining tables."
• (British) The hinged rear door of a hatchback.
• (US) Ellipsis of tailgate party.
  "The website was created by Harry St. John, a former college athlete who wanted to take the agony out of managing tailgates."
• (mining) A tunnel for drawing spent air away from the working face of a mine.

verb

• (automotive, intransitive, transitive) To drive dangerously close behind another vehicle.
  "That idiot has been tailgating me for the last five minutes."
• (finance, of a broker) To privately purchase or sell a security immediately after trading in the same security for a client.
• (US, intransitive) To have a tailgate party.
  "“Hey, what are you guys doing?” “Dude, we're gonna tailgate the tryouts.” “Oh, shit. That's a good idea. Oh, you gonna bust out Green Man, bro?” “No. No Green Man.” “What's Green Man?” “Well, in high school, Charlie was like our school mascot.” “A mascot nobody wanted. He'd get wasted and dress in this green spandex bodysuit.” “Spandex?” “It was really sad.” “That's it.” “You gotta bring the Green Man suit.” “Yeah, no. Done with it.” “The spandex.” “Green Man was good. It got me through some hard times. But I'm done with it. Tell you what. You can wear it if you want, but I'm just gonna be relaxing, okay? This is gonna be about chilling out for me.” “No. This is gonna be exactly like Woodstock.”"