What does “make a killing” mean?
The phrase “make a killing” or “made a killing” (past tense) is used to refer to making a lot of money doing some activity – whether it’s in the stock market, through a business, or whatever that activity may be.
Here’s an example of the usage of “make a killing”:
“Make A Killing” In a Sentence
"I hear that Bob made a killing investing in Microsoft stock in the 90's. He must have made 10 million dollars!"