The boomerang child phenomenon has become so commonplace (and the term so commonly used) that “boomerang child” has made it into the latest edition of the Merriam-Webster Collegiate Dictionary. Here’s their definition: “a young adult who returns to live at his or her family home especially for financial reasons.” According to Merriam-Webster, the term was first used in 1988.
The Urban Dictionary, Investopedia, and Wikipedia have definitions of boomerang children, boomerang, and the boomerang generation, respectively, but I believe this is the first time the term has made it into a “serious,” print-based dictionary. It looks like both the trend, and the term, are here to stay.