1In sports, a call meaning a ball is outside the line or a play is ruled out (e.g., in tennis).
テニスでそのボールはアウトだった。
That ball was out in tennis.
2In baseball, an out (a batter or runner being put out) or the number of outs.
そのピッチャーは三人で三アウトを取った。
That pitcher got three outs on three batters.
3Meaning 'outer' or 'external' — used to indicate the outside in compounds or technical contexts (derived from English 'out').
機械のアウト側に取り付けられた部品が壊れている。
The part mounted on the outside of the machine is broken.
4Used as 'OUT' on signs to indicate an exit (e.g., parking lot signs).
駐車場の看板に大きくOUTと書いてあった。
The parking sign had a big 'OUT' written on it.
5In golf, colloquially 'out' can refer to the front nine (the first nine holes).
今日はアウトを回ったので後半はゆっくりしよう。
We played the front nine today, so let's take it easy in the back nine.
6Colloquially used to mean 'no good,' 'unacceptable,' 'disqualified,' or 'finished' (e.g., 'That's out').
その発言は完全にアウトだよ。
That remark is totally out / unacceptable.
規定違反でチームはアウトになった。
The team was disqualified for violating the rules.
7Used as an abbreviation for check-out time (e.g., hotel check-out).
ホテルのアウトは午前11時です。
The hotel's check-out time is 11 a.m.