Regardless, a.
1. Having no regard; heedless; careless; as, regardless of life, consequences, dignity. Regardless of the bliss wherein he sat. Milton.
2. Not regarded; slighted. [R.] Spectator.
Syn. -- Heedless; negligent; careless; indifferent; unconcerned; inattentive; unobservant; neglectful. -- Re*gard"less*ly, adv. -- Re*gard"less*ness, n.
Shades of meaning
Fernald lists regardless only as an antonym, under eager.
He lists it without comment; the entries above explain its neighbors.
Synonyms
none given