Heedless, a.
Without heed or care; inattentive; careless; thoughtless; unobservant. O, negligent and heedless discipline! Shak. The heedless lover does not know Whose eyes they are that wound him so. Waller. -- Heed"less*ly, adv. -- Heed"less*ness, n.
Shades of meaning
Fernald has no entry of its own for heedless; he lists it under abstracted.
He lists it without comment; the entries above explain its neighbors.