Blithe

прилагательное [поэтическое] 1) весёлый, жизнерадостный, счастливый Синоним(ы): convivial, ebullient, elated, genial, jovial, light-hearted, cheerful Антоним(ы): dismal, gloomy, ill-humoured, melancholic, morose, sad, sullen, tranquil 2) небрежный, несерьёзный Синоним(ы): casual, heedless

Большой англо-русский словарь

Blithe

adjective (blither; blithest) Etymology: Middle English, from Old English blīthe; akin to Old High German blīdi joyous 1. of a happy lighthearted character or disposition 2. lacking due thought or consideration; casual, heedless Example: blithe unconcern Synonyms: see merryblithely adverb

Merriam-Webster's Collegiate Dictionary