In my youth to flip a car meant you rolled it. It could be a half-roll onto its top, a complete roll back onto its wheels, or it could be rolled over several times.
One smart-ass teenaged kid I knew flipped his car one night, and (according to him) when his grandfather who he lived with asked how the accident happened, this kid said he didn’t know how it happened, he was driving down the road and it “just flipped”.
I know that this is a zombie, but I happen to know what this means from my English major days.
“Flipping trains” meant playing at the trainyard, running the length of them, jumping around on the cars, from open door to open door, or from top to top. Trains would be slowly moving around from time to time, and the one you were playing on could suddenly start moving, causing you to lose your balance and fall off.
Kids who were exceptionally bad at risk/reward assessment sometimes jumped from moving train to moving train, and then slipped, and got caught under a moving train.
The H.T. Webster cartoon was basically a PSA about the dangers of this activity, which was universally forbidden, and the rule universally ignored.
In the university town where I went to college, flipping cars was what happened to cars left unattended too close to frats and other student housing on nights like little 5 weekend, when the alcohol consumption is like the night of the day the 21st amendment was passed. Friend of mine had a car that was a total lemon. He kept saying he was going to park it in Varsity Villas little 5 weekend, and paint “Turn me over” on top of it.
I would imagine in those circumstances it would be flipping car, not cars. Unless grandpa was stupid enough to let him have another car.
I went to college with a guy whose dad was an pretty good mechanic and fixed up cars. He’d buy a car, do some necessary repairs, and sell it. rinse and repeat. I assume that’s “flipping” cars, equivalent of flipping houses. He was making pretty good money at it, and the province came along and told him because he’d sold 8 cars in one year (I think it was) he had to apply for a car dealer permit and meet assorted other regulations. By the time I met this kid, his dad owned the local Volvo dealership and the kid got to drive a Volvo to and from school.
But yes, every description is valid lacking context: damn cars, reselling cars, rolling cars in accidents or overturning parked ones for fun.