From deo; a slave (literal or figurative, involuntary or voluntary; frequently, therefore in a qualified sense of subjection or subserviency) -- bond(-man), servant.
see GREEK deo
1. a slave, bondman, man of servile condition;
a. properly: opposed to ἐλεύθερος, 1 Corinthians 7:21; 1 Corinthians 12:13; Galatians 3:28; Ephesians 6:8; Colossians 3:11; Revelation 6:15; Revelation 13:16; Revelation 19:18; opposed to κύριος, δεσπότης, οἰκοδεσπότης, Matthew 10:24; Matthew 13:27; Luke 12:46; John 15:15 Ephesians 6:5; Colossians 3:22; Colossians 4:1; 1 Timothy 6:1; Titus 2:9, and very often.
b. metaphorically, α. one who gives himself up wholly to another's will, 1 Corinthians 7:23; or dominion, τῆς ἁμαρτίας, John 8:34; Romans 6:17, 20; τῆς φθορᾶς, 2 Peter 2:19, (τῶν ἡδονῶν, Athen. 12, p. 531 c.; τῶν χρημάτων, Plutarch, Pelop c. 3; τοῦ πίνειν, Aelian v. h. 2, 41). β. the δοῦλοι Χριστοῦ, τοῦ Χριστοῦ, Ἰησοῦ Χριστοῦ, are those whose service is used by Christ in extending and advancing his cause among men: used of apostles, Romans 1:1; Galatians 1:10; Philippians 1:1; 2 Timothy 2:24; Titus 1:1; James 1:1; 2 Peter 1:1; of other preachers and teachers of the gospel, Colossians 4:12; 2 Timothy 2:24; Jude 1:1; of the true worshippers of Christ (who is κύριος πάντων, Acts 10:36), Ephesians 6:6. The δοῦλοι τοῦ Θεοῦ, יְהוָה עַבְדֵי, are those whose agency God employs in executing his purposes: used of apostles, Acts 4:29; Acts 16:17; of Moses (Joshua 1:1), Revelation 15:3; of prophets (Jeremiah 7:25; Jeremiah 25:4), Revelation 1:1; Revelation 10:7; Revelation 11:18; of all who obey God's commands, his true worshippers, Luke 2:29; Revelation 2:20; Revelation 7:3; Revelation 19:2, 5; Revelation 22:3, 6; (Psalm 33:23 2. a servant, attendant, (of a king): Matthew 18:23, 26ff. (Synonym: see διάκονος.)