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leaving (a light, TV, etc.) on; leaving engaged (e.g. a key in a lock)
電気のつけっぱなしはダメだよ。
You shouldn't leave the lights on.
夫がテレビを付けっ放しで寝ていた。
My husband was sleeping with the TV left on.
ストーブの付けっ放しは火事の原因になるからやめよう。
Let's stop leaving the heater on, as it can cause a fire.