crazy crazy /ˈkreɪzi/

adjective

1. () Affected with madness or insanity  ( brainsick , demented , disturbed , crazy , mad , sick , unbalanced , unhinged )
   affected with madness or insanity
    A man who had gone mad
   a man who had gone mad
   
2. () Foolish; totally unsound  ( half-baked [Informal] , screwball [Informal] , softheaded , crazy , wiggy [Informal, American] )
   foolish; totally unsound
    A crazy scheme
   a crazy scheme
    Half-baked ideas
   half-baked ideas
    A screwball proposal without a prayer of working
   a screwball proposal without a prayer of working
   
3. () Possessed by inordinate excitement  ( crazy )
   possessed by inordinate excitement
    The crowd went crazy
   the crowd went crazy
    Was crazy to try his new bicycle
   was crazy to try his new bicycle
   
4. Intensely enthusiastic about or preoccupied with  ( crazy , dotty [Informal] , gaga [Informal] , wild )
   intensely enthusiastic about or preoccupied with
    Crazy about cars and racing
   crazy about cars and racing
    They are dotty about each other
   they are dotty about each other
    Gaga over the rock group's new album
   gaga over the rock group's new album
   
5. Bizarre or fantastic  ( crazy )
   bizarre or fantastic
    Had a crazy dream
   had a crazy dream
    Wore a crazy hat
   wore a crazy hat
   

noun

1. Someone deranged and possibly dangerous  ( crazy , looney , loony , nutcase , weirdo )
   someone deranged and possibly dangerous