WordWeb Online

1. Without care or concern
   "carelessly raised the children's hopes without thinking of their possible disappointment";
   - heedlessly
    
2. Without caution or prudence
   "one unfortunately sees historic features carelessly lost when estates fall into unsympathetic hands";
   - incautiously
    
3. In a rakish manner
   "she wore her hat carelessly at an angle";
   - rakishly, raffishly

Antonym: carefully