without reason, sense or good judgement; silly
nonsensical, idiotic
Cases of word usage
1) mad; foolish (barmy)
2) a foolish mistake (blunder)
3) a person (especially in a circus or pantomime) who makes a living by dressing up and doing foolish or funny things (clown)
4) silly; foolish (daft)
5) foolish (and showing self-importance) (fatuous)
6) a foolish behaviour; a foolish act, idea or word (foolery)
7) a foolish person; ( not now used) a person with very low intelligence (imbecile)
8) a male ass; a foolish person (jackass)
9) (any of many kinds of) small brown songbird; a bit of fun; to be foolish and waste time (lark)
10) a foolish person (lunatic)