Make a killing is an idiomatic expression that means to earn a huge profit or to be very successful in a particular enterprise or investment. Other synonyms include: rake it in, strike it rich, hit the jackpot, cash in, turn a tidy profit, clean up, strike gold, reap rewards, and make a fortune. These phrases suggest obtaining a large sum of money through a fortunate chance or timely skill. Each phrase implies the idea of achieving success through financial gain. While make a killing is a popular expression with a negative connotation, its synonyms paint a more positive picture of earning a substantial amount of money through hard work, timing, and luck.