Reckless, a. — Webster enters it under “reckless”
Etymology: [AS. recceleás, receleás.]
1. Inattentive to duty; careless; neglectful; indifferent. Chaucer.
2. Rashly negligent; utterly careless or heedless. It made the king as reckless as them diligent. Sir P. Sidney.
Syn. -- Heedless; careless; mindless; thoughtless; negligent; indifferent; regardless; unconcerned; inattentive; remiss; rash. -- Reck"less*ly, adv. -- Reck"less*ness, n.
Shades of meaning
Fernald has no entry of its own for recklessness; he lists it under temerity.
Where he writes about it:
Venturesomeness dallies on the edge of danger and experiments with it; foolhardiness rushes in for want of sense, heedlessness for want of attention, rashness for want of reflection, recklessness from disregard of consequences. — from temerity