The generation of people born between the 1950s and early 1970s, who were anarchic and directionless.
The term is first recorded in the December 1952 edition of Holiday:
"What, you may well ask, is Generation X? These are the youngsters who have seen and felt the agonies of the past two decades, who are trying to keep their balance in the swirling pressures of today, and who will have the biggest say in the course of history for the next 50 years."
Charles Hamblett and Jane Deverson's 1964 novel Generation X portrays the children who would come of age in the closing years of the 20th century:
"The ultimate responsibility of Generation X is to guide the human race through the final and crucial decades of this explosive century into the enlightenment of the next one."
The term became widespread in the late 80s and early 90s following Douglas Copeland's 1991 book - Generation X: tales for an accelerated culture.
See other phrases that were coined in the USA.