Light-hearted, a. — Webster enters it under “light-hearted”
Free from grief or anxiety; gay; cheerful; merry. -- Light"-heart`ed*ly, adv. -- Light"-heart"ed*ness, n.
Shades of meaning
Fernald lists light-heartedness only as an antonym, under anxiety.
He lists it without comment; the entries above explain its neighbors.
Synonyms
none given