A suffix attached to the masu-stem of verbs indicating something has been left in an improper state (e.g., 'left on/unfinished').
電気をつけっぱなしにして出かけた。
I left the light on and went out.
窓を開けっぱなしにしないでください。
Please don't leave the window open.
プリンターをつけっぱなしで節電にならない。
Leaving the printer on wastes electricity.
A suffix meaning '(doing) continuously' or 'keeps doing' — indicates an action is ongoing without stopping.
彼は映画を見て笑いっぱなしだった。
He kept laughing while watching the movie.
友達と夜通し話しっぱなしで寝不足だ。
I talked with friends all night and am sleep-deprived.
娘は文句を言いっぱなしで全然手伝わない。
My daughter keeps complaining and doesn't help at all.