noun
side out; gaining the right to serve
In volleyball and similar sports, when the receiving team wins the rally and gains the right to serve.
相手チームのミスでサイドアウトになった。
We got a side out due to the opposing team's mistake.
noun
ball going over the sideline
In tennis, when the ball lands outside the sideline, resulting in a fault or loss of point.
彼のショットはサイドアウトでポイントを失った。
His shot went side out and he lost the point.