lover, especially a man who is a promiscuous and unscrupulous lover
"In stepped [Justin] Bieber, with his mop of hair and an impish personality that seems to be part Dennis the Menace and part teenage Casanova." Andy Downing, Chicago Tribune, March 25, 2010
About the word:
In the 1700s, Giacomo Girolamo Casanova was a spy, a clergyman, a gambler, and apparently a man of charm. He was also a writer. His autobiographical musings about his more than 100 lovers made his name a byword for a man who loves too much.