Definitions of offhanded:

• adjective:   casually thoughtless or inconsiderate
• adjective:   with little or no preparation or forethought

  Example: "Trying to sound offhanded and reassuring"

• adverb:   in a casually inconsiderate manner

  Example: "She threw him over offhandedly without even a Dear-John letter"

• adverb:   without previous thought or preparation

  Example: "She had made these remarks offhandedly"