Denshi Jisho — Online Japanese dictionary

un-; non-; negative prefix
Prefix 
1: un-; non-;
2: bad ...; poor ...
Prefix 

You can also

Look up kanji details for *不.

Try a Yahoo Jisho search for *不 .
Try a Goo Jisho search for *不 .
Try a Google search for *不 .