1) Abstractedly 2) Carelessly 3) Hastily 4) Heedlessly 5) Inconsiderately 6) Irresponsibly 7) On impulse 8) Stupidly 9) Unthinkingly 1) Carelessly 2) Ignorantly 3) In a thoughtless manner 4) Insensitively 5) Neglectfully 6) Obliviously 7) Rashly 8) Recklessly 9) Selfishly 10) Showing thoughtlessness 11) Unthinking 12) Unthinkingly 
[adv] - in a thoughtless manner 2. [adv] - showing thoughtlessness
unthinking adverb in a thoughtless manner; `he stared thoughtlessly at the picture` adverb showing thoughtlessness; `he treated his parents thoughtlessly`