Denshi Jisho — Online Japanese dictionary

太る ふとる to grow fat (stout, plump); to become fat; to gain weight
Common word, Godan verb with ru ending, Intransitive verb 

You can also

Look up kanji details for 太る.

Try a Yahoo Jisho search for 太る .
Try a Goo Jisho search for 太る .
Try a Google search for 太る .