Denshi Jisho — Online Japanese dictionary

乱れる みだれる 1: to be disordered; to be disarranged; to be disarrayed; to be disheveled; to be dishevelled;
2: to be discomposed; to be upset; to get confused; to be disturbed;
3: to lapse into chaos (due to war, etc.)
Common word, Ichidan verb, Intransitive verb 

You can also

Look up kanji details for 乱れる.

Try a Yahoo Jisho search for 乱れる .
Try a Goo Jisho search for 乱れる .
Try a Google search for 乱れる .