開けっぱなし

left open; left ajar

開け open + っぱなし leave ~ undone or in a continued state
noun Rare #33,590
left open; left ajar Describes something that has been left open, often implying carelessness or that it should have been closed.
JA: ドアは開けっぱなしだった。
EN: The door was left open.

昔はどの家もドアは開けっぱなし

Back in the day, every house left its doors wide open.

— グッドフェローズ (1990)

窓を開けっぱなしにしておくべきではない

You shouldn't leave the window open.

窓が開けっぱなしだった

The window had been left open.

玄関開けっぱなし

The front door is left open.

— REC / レック (2007)

窓が開けっぱなしだったわよ

You left the window open.