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
   - rakishly, raffishly

See also: careless

Antonym: carefully