negligent
characterized by undue lack of attention or concern
With his usual scant sympathy, Arthur, hardly glancing aside at him, gave a lofty negligent little nod by way of recognition, and was passing on.
— Werner, E. T. C. (Edward Theodore Chalmers)
negligible
so small as to be meaningless; insignificant
The changes that have taken place in human nature during the historic period are so slight as to be practically negligible.
— Cohen, Chapma