To throw into disorder, disarrange, disturb order or peace; to disrupt or make things messy (also to dishevel, as with hair).
彼の突然の発言が会議の進行を乱した。
His sudden remark disrupted the progress of the meeting.
強い風が並んでいる本を乱してしまった。
A strong wind disarranged the books lined up.
そんなことで心を乱すな。
Don't let such things disturb you.