blithe in WordNet English dictionary

1. carefree and happy and lighthearted
   "was loved for her blithe spirit"; "a merry blithesome nature"; "her lighthearted nature"; "trilling songs with a lightsome heart"
   blithe  blithesome  lighthearted  lightsome  light-hearted 
   
2. lacking or showing a lack of due concern
   "spoke with blithe ignorance of the true situation"
   blithe