blithe 
/ˈblaɪθ, ˈblaɪð/ adjective
blith·er; blith·est /ˈblaɪθ, ˈblaɪð/ adjective 1 : showing a lack of proper thought or care : not caring or worrying
▪ He showed blithe disregard for the rights of others. ▪ He was blithe about the risks to his health. 2 literary : happy and without worry : carefree
▪ a blithe spirit ▪ blithe enjoyment
▪ He showed blithe disregard for the rights of others. ▪ He was blithe about the risks to his health.
▪ a blithe spirit ▪ blithe enjoyment
— blithe·ly adverb
▪ They blithely assumed there would be someone there to help them.
▪ They blithely assumed there would be someone there to help them.
