窓を開けっ放し

leave the window open

→ 窓
phrase Rare #33,628
leave the window open 開けっ放し means leaving something open, often with the implication that it should have been closed or that this is undesirable. It can be followed by にする or にしておく.
JA: 窓を開けっ放しにしないで。
EN: Don't leave the window open.

寝室の窓を開けっ放ししないでちょうだい

Please don’t leave the bedroom window open.

彼女は窓を開けっ放しにした

She left the window open.

夏はいつも窓を開けっ放し寝る

I always sleep with the windows open in summer.

窓を開けっ放ししておく

Don't leave the window open.

誰かが窓を開けっ放ししていたに違いないんだ

Someone must have left the window open.