The term "flagship killer" is a popular expression used in the smartphone industry to describe a device that offers high-end features and performance, often at a lower price point than its flagship counterparts. This type of phone typically has top-of-the-line hardware specifications such as powerful processors, large displays, advanced camera systems, and long battery life - all the things you would expect from an expensive flagship device but without the premium branding or high cost. In other words, a "flagship killer" is a phone that offers top-notch performance while undercutting its competitors in terms of price, making it a popular choice for consumers who want to get the most bang for their buck.