Careless, a.
Etymology: [AS. cearleás.]
1. Free from care or anxiety. hence, cheerful; light-hearted. Spenser. Sleep she as sound as careless infancy. Shak.
2. Having no care; not taking ordinary or proper care; negligent; unconcerned; heedless; inattentive; unmindful; regardless. My brother was too careless of his charge. Shak. He grew careless of himself. Steele.
3. Without thought or purpose; without due care; without attention to rule or system; unstudied; inconsiderate; spontaneouse; rash; as, a careless throw; a careless expression. He framed the careless rhyme. Beatie.
4. Not receiving care; uncared for. [R.] Their many wounds and careless hatms. Spemser.
1 more senses
Syn. -- Negligent; heedless; thoughtless; unthinking; inattentive; incautious; remiss; forgetful; regardless; inconsiderate; listless.
Shades of meaning
Fernald lists careless only as an antonym, under eager, inquisitive, vigilant.
He lists it without comment; the entries above explain its neighbors.