Thayer's Greek Lexicon

 1. he to whom a person or thing belongs, about which he has
power of deciding; master, lord
  1) the possessor and disposer of a thing
1a1. the owner; one who has control of the person, the master
1a2. in the state: the sovereign, prince, chief, the Roman emperor
  2) is a title of honour expressive of respect and reverence,
with which servants salute their master
  3) this title is given to: God, the Messiah

For Synonyms see entry G5830