Denshi Jisho — Online Japanese dictionary

痩せる やせる 1: (Usually written using kana alone) to become thin; to lose weight; to reduce (one's) weight; to slim;
2: to be barren; to be infertile; to be sterile
Common word, Ichidan verb, Intransitive verb 

You can also

Look up kanji details for 痩せる.

Try a Yahoo Jisho search for 痩せる .
Try a Goo Jisho search for 痩せる .
Try a Google search for 痩せる .