1 not taking care or paying attention.
2 unthinking, insensitive.
3 done without care; inaccurate.
4 light-hearted.
5 (foll. by of) not concerned about; taking no heed of.
6 effortless.
Derivatives:
carelessly adv. carelessness n.
Etymology: OE carleas (as CARE, -LESS)
Useful english dictionary. 2012.