Time to ask the hive mind for a new word to describe when you see people driving with their gas-cap door open. A couple years ago I asked the Internet for a Sniglet to describe when, typically real estate agents or online dating site patrons (aren't they essentially the same?), use long outdated photos of themselves. This yielded the gem verb or noun: "staleface." I hope we can do it again.
This can be complicated.  The most common configuration is only the door hanging, looking absent minded.  Or  you can have both door and cap hanging out.   Conceivably you can have door half way closed on the cord, choking the dangling cap.
gasajar or gas ajar If I have to explain it, just move on.
Robert said: The most common configuration is only the door hanging, looking absent minded.  Or  you can have both door and cap hanging out.   Conceivably you can have door half way closed on the cord, choking the dangling cap.
It can get even more complicated. I've seen a car with a section of gas pump hose trailing behind, nozzle apparently still in filler hole. Those hoses are designed to break off at a special link to prevent damage to the pump housing itself. And not all gas caps are attached by a tether ... the one on my 2000 CRV has no tether, so I set it on the roof while filling up. Forgot to replace it once and drove off. Lost it somewhere between the gas station and home. I'm not sure a single Sniglet could cover all those configurations. But ...
I nonetheless suggest: gasgaffe
Heimhenge said
I nonetheless suggest: gasgaffe
And, I am going to play off that and suggest: gaffe door.