Usually a person who uses others for dating entertainment, only. They pride themselves on playing the mating game, & the chase, vs. having a quality long-term relationship with someone. It's not about finding a special someone or helping to make that person's life happier. It's about conquest building to make themselves feel better.
A player usually is a mean term to say about someone (generally a guy) who goes from person to person, having sex and kissing them, dumps them, then moves onto someone else, then someone else, over and over and over and over and over again... ew