a reckless unprincipled person; an incorrigible rascal
"He refused ever to work, borrowed money on his father's credit, which he never returned, passed bad checks; was, in short, an out-and-out good-for-nothing scapegrace." Helen Warburton, "Jerry" in The Smart Set, January 1916
"[Graham] Greene, [Pico] Iyer wrote ... was 'a self-styled scapegrace' who openly confessed in his works to an endless list of 'treacheries and transgressions' and stirred compassion in his readers both for his undisguised grief at his own failings and for his efforts to forgive both betrayers and the betrayed." Liesl Schillinger, New York Times, December 30, 2011
About the Word:
Scapegrace may come from the notion of escaping (scape meaning "to escape") the grace of God. However serious that sounds, scapegrace, like scamp, is often used lightheartedly.