Holman Bible Dictionary 
Numbers 12:7 Deuteronomy 7:9
In the New Testament the adjective “faithful” is a derivative of the Greek noun meaning “faith.” Here we get the translation “faithful” as a natural derivative of faith. Once again the fundamental meaning is that the one so described is trustworthy and loyal. The root idea is that one has fidelity toward another person or toward God. For example, in 1 Corinthians 7:25 Paul commended himself to the Corinthians as one who is “faithful” (KJV) or “trustworthy” (NAS). In Revelation 2:10 the church in Smyrna and subsequent readers are commanded “be thou faithful unto death.” And, in Ephesians 1:1 Paul addressed the letter “to the faithful in Christ Jesus.” In other cases, however, “faithful” describes God's mode of relation toward persons or toward God's creation.
Many of these passages speak of God as faithful in order to comfort and encourage Christians. “If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness” ( 1 John 1:9 ). “God is faithful, who will not suffer you to be tempted above that ye are able” ( 1 Corinthians 10:13 ). “Faithful is he that calleth you, who also will do it” ( 1 Thessalonians 5:24 ).
The faithful person is steadfast, unchanging, and thoroughly grounded in relation to the other. This sort of fidelity, or faithfulness, is used in both the Old Testament and the New Testament to describe God's relation to the world and to describe the quality of relationship that Israel and Christians are called upon to have with God and with one another. See Faith; Trust; Trustworthy.
William L. Self
Morrish Bible Dictionary 
aman, πιστός.This word in both the O.T. and the N.T. is from the same root as 'faith.' It is being true to oneself, to one's nature, to any promise given, and to any trust committed. It is in various connections often applied to God Himself. Deuteronomy 7:9; Isaiah 49:7; 1 Corinthians 1:9 1 Corinthians 10:13; 1 Thessalonians 5:24; 2 Timothy 2:13; Hebrews 10:23; 1 Peter 4:19; 1 John 1:9 . The Lord Jesus also is faithful. He is 'a faithful high priest' and 'a faithful and true witness.' 2 Thessalonians 3:3; Hebrews 2:17; Revelation 1:5; Revelation 3:14; Revelation 19:11 . The commandments and testimonies of God are called faithful. Psalm 119:86,138 . The words of the gospel are also faithful: the promises attached thereto will unquestionably be fulfilled. 1 Timothy 1:15; 1 Timothy 4:9; 2 Timothy 2:11; Titus 3:8; Revelation 21:5 . Christians are exhorted to be faithful as stewards to any trust committed to them, and faithful as witnesses to an absent Lord. "Be thou faithful unto death, and I will give thee a crown of life." Revelation 2:10 .
Hawker's Poor Man's Concordance And Dictionary 
After what hath been said under the foregoing article of faith, I shall not think it necessary to add much on the subject of faithfulness. The sense of it is very obvious. I only beg to observe, that it appears from Scripture the Lord delights to be known to his people, in his covenant engagements, by this distinguishing perfection. That sweet passage delivered to the church by Moses, is a most decided proof of it: "Know, therefore, that the Lord thy God, he is God; the faithful God, which keepeth covenant and mercy with the that love him and keep his commandments to a thousand generations." Deuteronomy 6:9. See also 1 Samuel 2:34; 1 Corinthians 1:9; 1 Thessalonians 5:24; Revelation 1:5; Rev 19:11
King James Dictionary 
1. Firm in adherence to the truth and to the duties of religion.
Be thou faithful unto death, and I will give thee a crown of life. Revelation 2 .
2. Firmly adhering to duty of true fidelity loyal true to allegiance as a faithful subject. 3. constant in the performance of duties or services exact in attending to commands as a faithful servant. 4. Observant of compact, treaties, contracts, vows or other engagements true to one's word. A government should be faithful to its treaties individuals, to their word. 5. True exact in conformity to the letter and spirit as a faithful execution of a will. 6. True to the marriage covenant as a faithful wife or husband. 7. Conformable to truth as a faithful narrative or representation. 8. Constant not fickle as a faithful lover or friend. 9. True worthy of belief. 2 Timothy 2 .
Easton's Bible Dictionary 
Acts 10:45 16:1 2 6:15 Colossians 1:2 1 Timothy 4:3,12 5:16 6:2 Titus 1:6 Ephesians 1:1 1 Corinthians 4:17
It is used also of God's word or covenant as true and to be trusted ( Psalm 119:86,138; Isaiah 25:1; 1 Timothy 1:15; Revelation 21:5; 22:6 , etc.).
American Tract Society Bible Dictionary 
In many passages in the Bible, means "believing." Thus in Galatians 3:9 , believers are said to be blessed with Abraham, because of his preeminent distinction above all man for steadfast faith in God. This appellation is given in Scripture to true Christians, to indicate not only their saving faith in Christ, but their trustworthy and consistent Christian character, Acts 16:15 1 Corinthians 4:17 Ephesians 6:21 Colossians 4:9 1 Peter 5:12 . "A faithful saying" is one that cannot prove false, 1 Timothy 1:15 2 Timothy 2:11 .
Webster's Dictionary 
(1): ( a.) Worthy of confidence and belief; conformable to truth ot fact; exact; accurate; as, a faithful narrative or representation.
(2): ( a.) Full of faith, or having faith; disposed to believe, especially in the declarations and promises of God.
(3): ( a.) True and constant in affection or allegiance to a person to whom one is bound by a vow, be ties of love, gratitude, or honor, as to a husband, a prince, a friend; firm in the observance of duty; loyal; of true fidelity; as, a faithful husband or servant.
(4): ( a.) Firm in adherence to promises, oaths, contracts, treaties, or other engagements.
Cyclopedia of Biblical, Theological and Ecclesiastical Literature 
1. A title given in Scripture to Christians ( 1 Corinthians 4:17; Ephesians 6:21, et al.).
2. The term, Πιστοὶ , The Faithful (FIDELES), was the general and favorite name in the early Church to denote baptized persons. By this name they were distinguished, on the one hand, from the Ἄπιστοι , such as were not Christians; and, on the other, from the catechumens. -Bingham, Orig. Eccl. book 1, chapters 3, 4; Riddle, Christian Antiquities, book 2, chapter 5.
- Faithful from Holman Bible Dictionary
- Faithful from Morrish Bible Dictionary
- Faithful from Hawker's Poor Man's Concordance And Dictionary
- Faithful from King James Dictionary
- Faithful from Easton's Bible Dictionary
- Faithful from American Tract Society Bible Dictionary
- Faithful from Webster's Dictionary
- Faithful from Cyclopedia of Biblical, Theological and Ecclesiastical Literature