Cavalier means haughty or arrogant.
Cavalier is a adjective.
Synonyms: arrogant, offhand, uncaring, disdainful, cocky, uncaring.
Antonyms: caring, sincere, thoughtful, diligent, considerate.
Note: Cavalier can also be a noun meaning a horseman or someone with the bearing or manner of a knight or gentleman.
One must try to be more conscientious and less cavalier.
Mr. Ravi's cavalier treatment towards his friends only solidified his reputation as an arrogant person.