1Safe, all right, or fine — describing a state free of danger or problems; also used to say one's health or a situation is okay.
転んだけど、大丈夫、けがはしていない。
I fell, but I'm fine — I'm not hurt.
この橋は古いけど、まだ大丈夫だと専門家が言った。
The bridge is old, but experts say it's still safe.
熱はもう大丈夫ですか。
Is your fever all right now?
パスワードを忘れても大丈夫、後で再設定できる。
It's fine even if you forget your password — you can reset it later.
2An older adverbial usage meaning "certainly" or "without doubt"; rarely used in modern conversation.
先生が太鼓判を押したのだから、大丈夫成功するだろう。
Since the teacher personally vouched for it, it will surely succeed.
3A colloquial way to decline an offer or invitation, or to reassure someone that there's no need to worry — similar to "no thanks" or "it's okay."
もう一杯どう？ ううん、大丈夫。
Want another glass? No, I'm good.
タクシーを呼ぼうか？ 大丈夫、歩いて帰れるから。
Should I call a taxi? No thanks, I can walk home.
手伝ってもらわなくても大丈夫だよ。
You don't need to help me, it's okay.
遅れてもいい? うん、大丈夫、気にしないで。
Is it okay if I'm late? Yeah, that's fine, don't worry about it.
4An archaic noun meaning a great, admirable, or manly figure; rarely used in modern Japanese.