Denshi Jisho — Online Japanese dictionary

Search for this in plain form: 面白い

面白半分 おもしろはんぶん for fun; half in jest
Na-adjective, Noun 

You can also

Look up kanji details for 面白半分.

Try a Yahoo Jisho search for 面白半分 .
Try a Goo Jisho search for 面白半分 .
Try a Google search for 面白半分 .