Not good; useless or broken — something that does not serve its purpose.
このプリンターは古くてもう駄目だ。
This printer is old and no longer works.
その説明では分かりにくくて駄目です。
That explanation is confusing and no good.
腕時計が水に濡れて駄目になった。
My watch got wet and became useless.
Hopeless; wasted — an action or effort that turns out to be in vain.
何時間待っても彼は来なかった。全部駄目だったよ。
No matter how long we waited, he didn't come. It was all for nothing.
あの試合は戦術が裏目に出て駄目に終わった。
That match ended badly — the tactics backfired and everything was wasted.
重要なデータを消してしまい、復元できなかったので作業は駄目になった。
I deleted important data and couldn't restore it, so the work was ruined.
Cannot; must not; not allowed — indicates prohibition or impossibility.
ここでタバコを吸うのは駄目です。
You must not smoke here.
まだ宿題が終わってないなら、ゲームは駄目だよ。
If your homework isn't finished yet, you can't play games.
あの高い棚には乗るのは危ないから駄目だ。
Don't climb on that high shelf — it's dangerous and not allowed.
In the game of go, a neutral point (a spot that belongs to neither player at the end).
その辺りに駄目が二つあるから、地合いは均衡している。
There are two dame (neutral points) around there, so the balance of territory is even.
Interjection: “No!” or “Stop!” — a short, colloquial exclamation expressing strong refusal or warning.
駄目！そんなにお酒を飲まないで。
No! Don't drink so much alcohol.
ダメ！そのボタンを絶対に押さないでください。
No! Please don't press that button under any circumstances.