martus or martur (3144) (whence Eng., "martyr," one who bears "witness" by his death) denotes "one who can or does aver what he has seen or heard or knows"; it is used (a) of God, <Rom. 1:9; 2 Cor. 1:23; Phil. 1:8; 1 Thes. 2:5,10> (2nd part); (b) of Christ, <Rev. 1:5; 3:14>; (c) of those who "witness" for Christ by their death, <Acts 22:20; Rev. 2:13; Rev. 17:6>; (d) of the interpreters of God's counsels, yet to "witness" in Jerusalem in the times of the Antichrist, <Rev. 11:3>; (e) in a forensic sense, <Matt. 18:16; 26:65; Mark 14:63; Acts 6:13; 7:58; 2 Cor. 13:1; 1 Tim. 5:19; Heb. 10:28>; (f) in a historical sense, <Luke 11:48; 24:48; Acts 1:8,22; 2:32; 3:15; 5:32; 10:39,41; 13:31; 22:15; 26:16; 1 Thes. 2:10> (1st part); <1 Tim. 6:12; 2 Tim. 2:2; Heb. 12:1>, "(a cloud) of witnesses," here of those mentioned in <ch. 11>, those whose lives and actions testified to the worth and effect of faith, and whose faith received "witness" in Scripture; <1 Pet. 5:1>.
(from Vine's Expository Dictionary of Biblical Words)
(Copyright (C) 1985, Thomas Nelson Publishers)