What does donjuan mean?

Don Juan was a fictional libertine, who appeared in several stories in the 17th century.
He was famed for his acrobatic talents which he used to climb the balconies of rich women; whom he seduced. The women often became his allies in his various misadventures. He was also a skilled sWordsman; which he often used to escape the angry husbands and boyfriends of the women he pursued.

Therefore a "Don Juan" is anybody who recklessly chases after women; particularly women who are already attached to other men.