Quick definitions from WordNet (offhanded)
▸ adjective: casually thoughtless or inconsiderate
▸ adjective: with little or no preparation or forethought ("Trying to sound offhanded and reassuring")
▸ adverb: in a casually inconsiderate manner ("She threw him over offhandedly without even a Dear-John letter")
▸ adverb: without previous thought or preparation ("She had made these remarks offhandedly")
▸ adjective: casually thoughtless or inconsiderate
▸ adjective: with little or no preparation or forethought ("Trying to sound offhanded and reassuring")
▸ adverb: in a casually inconsiderate manner ("She threw him over offhandedly without even a Dear-John letter")
▸ adverb: without previous thought or preparation ("She had made these remarks offhandedly")