A gambler is a person who takes a lot of high-risk chances. Your friends might call you a gambler if you spend your free time bungee jumping and playing high-stakes poker.
When you seek adventure or danger, you're gambling with your safety or even your life, which makes you one kind of gambler. Other gamblers enjoy betting money on sports, card games, or games of chance. Gambler came after gamble, "risk something of value on a game of chance," from the Middle English gammlen, "play or be merry," with its Old English root gamen, or "game."