Definition from Wiktionary, the free dictionary
stepgranddaughter (plural stepgranddaughters)
- The daughter of one's stepchild, or the stepdaughter of one's child.
2007 January 11, Dennis Hevesi, “Roberta Wohlstetter, 94, Military Policy Analyst, Dies”, New York Times:
- Besides her daughter, Joan, of Manhattan, surviving are a brother, Edmund S. Morgan of New Haven, a Pulitzer Prize -winning historian; and a stepgranddaughter.