a.
1.
Heedless, regardless, careless, neglectful, negligent, inattentive, inconsiderate, unmindful, unobservant, remiss, unwatchful, inadvertent, flighty, reckless, hare-brained, giddy-brained, light-headed, giddy.
2.
Stupid, dull, insensate, unthinking, blockish.
3.
Dissipated, gay, giddy, loose.