“Srila Prabhupada, what does it mean to be humble?” And his answer was really incredible. He said, “Humility means that you are convinced beyond any doubt that there is nothing in this world, absolutely nothing in this world, not your money, not your family, not your fame, not your gun, not your education, nothing that will save you except the mercy of Krishna. When you are convinced like this, then you are humble.”
Reference: Remembrances by Yadubara Das- Folio Vedabase