The Collaborative International Dictionary of English v.0.48:

Machiavelian \Mach`i*a*vel"ian\, Machiavellian
\Mach`i*a*vel"lian\, a. [From Machiavel (also called
   Machiavelli), an Italian writer, secretary and
   historiographer to the republic of Florence.]
   Of or pertaining to Machiavelli, or to his supposed
   principles for conduct of government, as enunciated in his
   tract The Prince; politically cunning; characterized by
   duplicity, political expediency, unscrupulous cunning, or bad
   faith; crafty.
   [1913 Webster +PJC] Machiavelian

The Collaborative International Dictionary of English v.0.48:

Machiavelian \Mach`i*a*vel"ian\, Machiavellian
\Mach`i*a*vel"lian\, n.
   One who adopts the principles of Machiavelli; a cunning and
   unprincipled politician.
   [1913 Webster] Machiavelism