1In baseball, a ruling that a runner has reached a base without being put out; a safe call.
内野ゴロで一塁に全力で走ったが、審判はセーフの判定だった。
He ran full speed to first on the grounder, but the umpire called him safe.
タッチプレーは微妙で、ビデオ判定の結果セーフになった。
The tag play was close, and after video review it was ruled safe.
2In sports such as tennis, a call that the ball landed within the court (equivalent to 'in').
ライン際のボールはぎりぎりセーフと判定された。
The ball near the line was judged just in.
審判がセーフを宣言すると、観客席から歓声が上がった。
When the umpire declared it in, cheers rose from the stands.
3Colloquial adjective-like term meaning 'all right', 'OK', 'acceptable', or 'in time'. Used informally.
ここまで来れば電車に間に合うからセーフだよ。
If you get here now you'll make the train, so it's safe/OK.
今日は宿題を忘れたけど、先生が許してくれたのでセーフだった。
I forgot my homework today, but the teacher forgave me, so it was OK.
その服、派手すぎるかと思ったけど結構セーフだね。
I thought that outfit might be too flashy, but it's actually OK.