Thayer's Greek Lexicon

 1. adversary (one who opposes another in purpose or act), the
name given to
  1) the prince of evil spirits, the inveterate adversary of
God and Christ
1a1. he incites apostasy from God and to sin
1a2. circumventing men by his wiles
1a3. the worshippers of idols are said to be under his control
1a4. by his demons he is able to take possession of men and
inflict them with diseases
1a5. by God's assistance he is overcome
1a6. on Christ's return from heaven he will be bound with chains
for a thousand years, but when the thousand years are
finished he will walk the earth in yet greater power, but
shortly after will be given over to eternal punishment
  2) a Satan-like man