Unconscious, a. — Webster enters it under “unconscious”
1. Not conscious; having no consciousness or power of mental perception; without cerebral appreciation; hence, not knowing or regarding; ignorant; as, an unconscious man. Cowper.
2. Not known or apprehended by consciousness; as, an unconscious cerebration. "Unconscious causes." Blackmore.
3. Having no knowledge by experience; -- followed by of; as, a mule unconscious of the yoke. Pope. -- Un*con"scious-ly, adv. -- Un*con"scious*ness, n.
Shades of meaning
Fernald has no entry of its own for unconsciousness; he lists it under stupor.
He lists it without comment; the entries above explain its neighbors.