Noun
Usually written in kana
1.  idiot;  moron;  fool
2.  trivial matter;  folly;  absurdity
Adjective (な)
Usually written in kana
3.  stupid;  foolish;  dull;  absurd;  ridiculous
Adjective (な)
Noun
Usually written in kana
4.  fervent enthusiast;  nut;  person singularly obsessed with something
usu. in compounds
Noun
Abbreviation
Usually written in kana
5.  Mactra chinensis (species of trough shell)