An oafish man prone to rambunctious behavior, despite having reached adulthood. The frequent subject of memes, the phrase is often linked to a family photo of American politician Mike Huckabee that includes his two literally large adult sons. Despite being 35 years old, my son is such a doofus. I can't believe I have a large adult son. My large adult sons just gave our dog a bath in the trunk of my car.