cavalier

Concise Oxford English Dictionary © 2008 Oxford University Press:
cavalier /ˌkavəˈlɪə/

▶noun

• 1 (Cavalier) historical a supporter of King Charles I in the English Civil War.

• 2 archaic or literary a courteous gentleman.

• 3 archaic a cavalryman.

▶adjective showing a lack of proper concern.

– derivatives
cavalierly adverb.

– origin C16: from Fr., from Ital. cavaliere, based on L. caballus ‘horse’.