(noun)
a man who is trained in horsemanship and in the bearing of arms, or a soldier mounted on a horse (a knight);
e.g. They were saved by a cavalier on a large black horse.
(noun)
in historical usage, a person who supported King Charles I of England in the English Civil War;
e.g. He was a Cavalier in his political leanings.
(noun)
a charming, attractive, and well-dressed man, especially one acting as a lady's dancing partner or escort;
e.g. Her cavalier took her arm and led her inside.
(noun)
a small dog breed, similar to a spaniel, with a long snout and floppy ears;
e.g. A cavalier puppy was playing on the grass.