a highly innovative, very powerful, or extremely useful computer application; esp one sufficiently important as to justify purchase of the equipment or software
killer app in American English
noun
a computer application that is so superior to its competitors that it dominates the market
Word origin
[1990–95]This word is first recorded in the period 1990–95. Other words that entered Englishat around the same time include: Megan's Law, Tejano, copay, family leave, macarena