A person who gambles, often with a connotation of a habitual or professional risk-taker. The English loanword carries a slightly more stylish or Western image compared to native terms like 博徒.
彼は生まれつきのギャンブラーだ。
He is a born gambler.
あのギャンブラーは一晩で大金を失った。
That gambler lost a fortune in one night.
He quit his job and became a gambler.
She is a professional gambler who makes a living playing card games.