Thayer's Greek Lexicon

 1. to serve for hire
2. to serve, minister to, either to the gods or men and used
alike of slaves and freemen
  1) in the NT, to render religious service or homage, to worship
  2) to perform sacred services, to offer gifts, to worship God in
the observance of the rites instituted for his worship
2b1. of priests, to officiate, to discharge the sacred office