killer appn /ˈkɪlər æp/ (also killer application) noun [countableC] 1.n a piece of technology on a new product, which is so good or useful that a lot of people buy the product 〔新产品的〕制胜法宝,卖点技术
2.na piece of computer software that many want to buy, especially one that works so well on a particular machine that people want to buy it