Synset

marked by blithe unconcern
<adj.all>   freq. cnt.: 4 freq. cnt.: 3 freq. cnt.: 1

casual

insouciant

nonchalant

sample sentences

"an ability to interest casual students"
"showed a casual disregard for cold weather"
"an utterly insouciant financial policy"
"an elegantly insouciant manner"
"drove his car with nonchalant abandon"
"was polite in a teasing nonchalant manner"