Denshi Jisho — Online Japanese dictionary

1: foolishness; silliness; stupidity; folly;
2: (Archaism) (Humble (kenjougo) language) I; me
Common word, Noun, Na-adjective 
うぐ stupid; ignorant
Na-adjective, Noun 
かぐ 1: very stupid (person); great fool;
2: (Humble (kenjougo) language) oneself
Noun 
ちぐ imbecility; idiocy
Noun 
あんぐ 1: imbecility; feeblemindedness;
2: dark
Na-adjective, Noun 
あんぐ 1: imbecility; feeblemindedness;
2: dark
Na-adjective, Noun 
がんぐ obstinate and foolish
Na-adjective, Noun 
けいぐ moronity; moron
Noun 
けんぐ the wise and the foolish
Noun 
たいぐ great folly or fool
Noun 
ぼんぐ common person; foolish commoner
Na-adjective, Noun 
ようぐ mediocrity; imbecility
Na-adjective, Noun 
しゅうぐ the vulgar masses
Noun 

You can also

Look up kanji details for *愚.

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