What EXACTLY is Gen Jones?

Is it the boomer/X cusp? Is it second wave boomers? Or is it simply boomer/X hybrid years?

Ive seen 1954-1965, but that makes zero sense, because 1965 is Gen X and 1954 is still first wave boomer. I have seen 1955-1960, but where does 1961-1964 then fall?

Should it simply be 1955-1964 (aka second wave boomers) or a numerical cusp (something like 1961-1966)?