Real Dictionary

Generation X in American English
the generation of persons born in the 1960s and 1970s, the children of the baby boomers, often variously regarded as apathetic, materialistic, irresponsible, etc.
noun: the generation born between the mid-1960s and the mid-1970s

Generation X in British English
noun: members of the generation of people born between the mid-1960s and the late-1970s, often perceived as being highly educated but underemployed, and lacking direction and disaffected in their younger years