From BiblePortal Wikipedia

Vine's Expository Dictionary of NT Words [1]

A — 1: Ἀντίδικος (Strong'S #476 — Noun Masculine — antidikos — an-tid'-ee-kos )

firstly, "an opponent in a lawsuit,"  Matthew 5:25 (twice);   Luke 12:58;  18:3 , is also used to denote "an adversary or an enemy," without reference to legal affairs, and this is perhaps its meaning in  1—Peter 5:8 , where it is used of the Devil. Some would regard the word as there used in a legal sense, since the Devil accuses men before God.

B — 1: Ἀντίκειμαι (Strong'S #480 — Verb — antikeimai — an-tik'-i-mahee )

is, lit., "to lie opposite to, to be set over against." In addition to its legal sense it signifies "to withstand;" the present participle of the verb with the article, which is equivalent to a noun, signifies "an adversary," e.g.,  Luke 13:17;  21:15;  1—Corinthians 16:9;  Philippians 1:28;  1—Timothy 5:14 . This construction is used of the Man of Sin, in  2—Thessalonians 2:4 , and is translated "He that opposeth," where, adopting the noun form, we might render by "the opponent and self-exalter against..." In  Galatians 5:17 it is used of the antagonism between the Holy Spirit and the flesh in the believer; in   1—Timothy 1:10 , of anything, in addition to persons, that is opposed to the doctrine of Christ. In these two places the word is rendered "contrary to." In the Sept. it is used of Satan,  Zechariah 3:1 , and of men,  Job 13:24;  Isaiah 66:6 . See Contrary , Oppose.

C — 1: Ὑπεναντίος (Strong'S #5227 — Adjective — hupenantios — hoop-en-an-tee'-os )

"contrary, opposed," is a strengthened form of enantios (en, "in," and antios, "set against"). The intensive force is due to the preposition hupo. It is translated "contrary to," in  Colossians 2:14 , of ordinances; in  Hebrews 10:27 , "adversaries." In each place a more violent form of opposition is suggested than in the case of enantios. See Contrary.

Hastings' Dictionary of the New Testament [2]

This renders three Greek words in the NT:

1. ἀντίδικος, properly an adversary in a lawsuit, and used of an earthly adversary in  Matthew 5:25,  Luke 12:58;  Luke 18:3 -all these with a legal reference. It is used of an enemy of God in  1 Samuel 2:10 (Septuagint), and in  1 Peter 5:8 of ‘ the enemy,’ Satan; in this last passage διάδολος is anarthrous, as a proper name, while ἀντίδικος has the article (see Devil and Satan).

2. ἀντικείμενος, used in  Luke 13:17 of our Lord’s Jewish opponents, and in  Luke 21:15 of all adversaries of the disciples, is employed by St. Paul to denote those who oppose the Christian religion, probably in all cases with the suggestion that the devil is working through them. Such are the ‘adversaries’ of  1 Corinthians 16:9,  Philippians 1:28; in  1 Timothy 5:14 Chrysostom takes the ‘adversary’ to be Satan, the ‘reviler’ (cf.  1 Timothy 5:15), or he may be the human enemy as prompted by Satan. In  2 Thessalonians 2:4 ‘he that opposeth’ (ὁ ἀντικείμενος) is Antichrist ( q.v. [Note: quod vide, which see.] ), whose parousia is according to the working of Satan ( 1 Timothy 5:9); and it is interesting to note that the letter of the Churches of Vienne and Lyons ( Historia Ecclesiastica (Eusebius, etc.)v. i. 5) uses this expression absolutely of Satan, or of Antichrist, working through the persecutors, and ‘giving us a foretaste of his unbridled activity at his future coming.’

3. ὑπεναντίος is used in  Hebrews 10:27 of the adversaries of God, apostates from Christ, probably with reference to  Isaiah 26:11, where the Septuaginthas the same word. A similar phrase in  Titus 2:8 is ‘he that is of the contrary part,’ an opponent, ὁ ἐξ ἐναντίας. In  Colossians 2:14 the word ὑπεναντίος is used of an inanimate object: ‘the bond … which was contrary to us.’

A. J. Maclean.

Hawker's Poor Man's Concordance And Dictionary [3]

This is a general name applied to all persons, in common, who have a controversy, or are at variance with each other. Thus the Lord saith to Israel, "I will be an adversary to thine adversaries." ( Exodus 23:22) And the prophet describes the Lord as an adversary to his people, in the day of his displeasure. "He hath bent his bow (saith he) as an enemy; he stood with his right hand as an adversary." ( Lamentations 2:4) And the Lord Jesus describes God the Father, as a law adversary, when he saith, ( Matthew 5:25) "Agree with thine adversary quickly, whilst thou art in the way with him." The Scriptures represent also Satan, as an adversary to Christ and his church. Thus Jesus, by the spirit of prophecy, saith, "Who is mine adversary? let him come near to me." ( Isaiah 50:8) And Zechariah ( Zechariah 3:1) represents Satan as "an adversary standing at Joshua's right hand, to resist him." And the apostle Peter calls the devil an adversary going about to devour; and chargeth the church to resist him steadfast in faith. ( 1 Peter 5:8) From these different views of the word, it will be very easy to learn, that the name of adversary is indiscriminately given to all persons who are in a state of controversy with each other, whether good or evil.

Wilson's Dictionary of Bible Types [4]

 Matthew 5:25 (b) The adversary in this portion evidently refers to GOD who sends His porter, death, to take men from this scene to the Judge, the Lord Jesus Being found guilty, the Lord JESUS hands this wicked sinner over to one of His angels who is the officer. The angel takes the lost sinner to hell, which is GOD's prison house. Since the prisoner can never pay the debt he must remain there forever.

 1 Timothy 5:14 (b) The adversary in this passage refers to critics of GOD's people who in their opposition to Christ are quick to find fault with GOD's people, and to call attention to the failures of Christians.

King James Dictionary [5]

AD'VERSARY, n. See Adverse.

1. An enemy or foe one who has enmity at heart.

The Lord shall take vengeance on his adversaries.  Nahum 1 .

In scripture, Satan is called THE adversary, by way of eminence.  1 Peter 5 .

2. An opponent or antagonist, as in a suit at law, or in single combat an opposing litigant.

AD'VERSARY, a. Opposed opposite to adverse. In law, having an opposing party, as an adversary suit in distinction from an application, in law or equity, to which no opposition is made.

Webster's Dictionary [6]

(1): (a.) Having an opposing party; not unopposed; as, an adversary suit.

(2): (n.) One who is turned against another or others with a design to oppose or resist them; a member of an opposing or hostile party; an opponent; an antagonist; an enemy; a foe.

(3): (a.) Opposed; opposite; adverse; antagonistic.

Easton's Bible Dictionary [7]

 1 Kings 5:4 11:14,23,25 Luke 13:17 Matthew 5:25 Luke 12:58 Luke 18:3 1 Peter 5:8

Holman Bible Dictionary [8]

 Psalm 38:20 Psalm 69:19 Psalm 71:13 Psalm 81:14 Psalm 109:29 1 Peter 5:8-9

Fausset's Bible Dictionary [9]

The meaning of Satan ( 1 Peter 5:8); also divine justice ( Luke 12:58-59).

Charles Buck Theological Dictionary [10]

One who sets himself in opposition to another: one of the names of Satan.

See Satan

Baker's Evangelical Dictionary of Biblical Theology [11]

See Satan

International Standard Bible Encyclopedia [12]

ad´vẽr - sa - ri , ad´vẽr - sā̄̇ - ri  : This word (in the singular or plural) is used in the Old Testament to render different Hebrew words. In thirty-two cases the word corresponds to the noun צר , cār , or the verb צרר , cārar ̌ . This noun is the ordinary word for "foe" or "adversary." In twelve passages the Hebrew word, of which "adversary" is the translation, is שׂטן , sāṭān = noun or שׂטן , sāṭan = verb. This stem means "to oppose," or "thwart" anyone in his purpose or claims.

The angel of Yahweh was sāṭān to Balaam ( Numbers 22:22 ). The word often denotes a political adversary ( 1 Kings 11:14 ,  1 Kings 11:23 ,  1 Kings 11:25 ). In four cases (namely, Prologue to Job;  Zechariah 3:1 ,  Zechariah 3:2;  1 Chronicles 21:1;  Psalm 109:6 ) the King James Version retains Satan as the rendering. But it is only in 1 Chronicles that the word is used without the article, that is, strictly as a proper name. The Septuagint gives διάβολος , diábolos , as the rendering, and both in Job and Zechariah, Satan is portrayed as the "false accuser." In two cases "adversary" represents two Hebrew expressions which mean the "opponent in a suit" or "controversy" ( Job 31:35;  Isaiah 50:8 ).

In the New Testament "adversary" represents: (1) αντικειμενοι , ἀντικείμενοι , antikeı́menoi , the participle of a verb which means "to be set over against," "to be opposed" ( Luke 13:17;  Philippians 2:8 ). (2) ἀντίδικος , antı́dikos , "opponent in a lawsuit," "prosecutor" ( Matthew 5:25;  Luke 12:58;  Luke 18:3;  1 Peter 5:8 ). According to the last passage the devil is the "accuser" or "prosecutor" of believers, but according to another writer they have an "advocate" or "counselor for the defense" with the Father ( 1 John 2:1 ). In one passage ( Hebrews 10:27 ) "adversary" represents a Greek word, hupenantı́os , which means "set over against," "contrary to" - a word used in classical Greek and in the Septuagint.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [13]

in Heb. properly שָׂטָן , Satan (i.e. Satan, as it signifies, when with the article), an opponent, e.g. in war, a Foe ( 1 Kings 5:18;  1 Kings 11:14; 23:25;  1 Samuel 29:4), in the forum, a Plaintiff ( Psalms 109:6; comp.  Zechariah 3:1-2), or generally a Resister ( 2 Samuel 19:23), as one that Blocks the way ( Numbers 22:23; comp.  Numbers 22:32). In Greek properly Ἀντίδικος , one who Speaks Against us, e.g. in a suit, the Complainant ( Matthew 5:25;  Luke 12:50); or, generally, an Enemy ( Luke 18:3), specially, the Devil ( 1 Peter 5:8). (See Accuser).