Source : Webster's Revised Unabridged Dictionary (1913)

Scalawag \Scal"a*wag\, n.
   A scamp; a scapegrace. [Spelt also {scallawag}.] [Slang,
   U.S.] --Bartlett.

Source : WordNet®

scalawag
     n 1: white Southerner supporting Reconstruction policies after
          the Civil War usually for self-interest [syn: {scallywag}]
     2: a deceitful and unreliable scoundrel [syn: {rogue}, {knave},
         {rascal}, {rapscallion}, {scallywag}, {varlet}]
     3: one who is playfully mischievous [syn: {imp}, {scamp}, {monkey},
         {rascal}, {rapscallion}, {scallywag}]