This is the 5976th most frequent Japanese word.
アウトー
"アウトー" is a slang term meaning "out of line" or "crossing the line" in behavior.
Here 'アウトー' (autoo) is used colloquially to proclaim that an action is unacceptable or inappropriate, borrowing from sports jargon where 'アウト' means out.
その行動は完全にアウトーだよ！
That action is completely out!
In this case, 'アウトー' is used in the sports context, where it literally means 'out' as in a player being out of play.
アウトーが宣告された選手は、グラウンドを去ります。
The player who was declared out leaves the field.
Here, 'アウトー' is treated as a named term, reflecting on its linguistic or cultural usage.