to refuse to believe: to reject a report or message as untrue and withhold trust from it
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This is the flat opposite of believing. It describes people who hear a report and turn it down as untrue, refusing to put their trust in it.
It shows up most memorably around the resurrection: when the risen Jesus was announced, even those who had followed him most closely could not bring themselves to accept it. The same word covers a settled refusal of the Christian message, whether from a crowd hearing it for the first time or from those who reject Christ as the cornerstone.
The related noun ἀπιστία names the state of unbelief, and the adjective ἄπιστος names the person who lives in it. The close verb ἀπειθέω sits right next to it but shifts the weight from refusing to believe toward refusing to obey.
to be unfaithful: to break faith and prove false to a commitment or to God
TranslatabilityApproximateCertaintySettled
Here the same verb turns from the head to the heart of a relationship. Because the Greek word for faith also means faithfulness, its opposite can mean not only "to disbelieve" but "to break faith," to prove false to someone you were bound to.
Paul uses it this way of Israel: some were unfaithful to God, yet their failure could not cancel God's own reliability. The point is sharpest in a line to Timothy, where being faithless is set directly against Christ remaining faithful, for even human unfaithfulness runs up against a God who cannot deny himself.
The line between this sense and plain disbelief is thin, because for these writers refusing to trust God and being disloyal to him are two sides of one failure.
The failure is one of credence: refusing to accept a report as true. The women's news of the resurrection struck the disciples as an idle tale, and they would not believe it.Luk 24:11Mrk 16:11
It shades into unfaithfulness, a breach of trust within a relationship rather than defiance of a command. Paul asks whether Israel's failure to keep faith cancels God's faithfulness, and reminds Timothy that "if we are faithless, he remains faithful."Rom 3:32Ti 2:13
It can be a wavering that lingers even amid gladness, not a hardened stance. The disciples "still disbelieved for joy" when Jesus stood among them, unable to credit what they were seeing.Luk 24:41
Both
Both name the negative response to the gospel and stand as the opposite of saving faith, each tied to whether a person receives life or condemnation.Jhn 3:36Mrk 16:16
In a single passage the two words describe the very same people who reject Christ the rejected stone, one word for their not believing and the next for their not obeying the word.1Pe 2:71Pe 2:8
The failure is one of the will: an active refusal to submit to what God commands or announces, not merely a mind left unconvinced. Paul sets it opposite obedience itself, describing people who "do not obey the truth but obey unrighteousness" and a "disobedient and contrary" nation.Rom 2:8Rom 10:21
This defiance can be organized and turned against others, stirring up hostility rather than staying a private state of mind. Luke reports that those who refused the message roused the Gentiles and poisoned the wider crowd.Act 14:2Act 19:9
It carries the weight of rebellion that forfeits God's promise and draws judgment, the settled refusal that kept a generation out of God's rest and perished the world of Noah's day.Heb 3:181Pe 3:20
ἀπιστίαthe noun for the state itself: unbelief or unfaithfulness, where this word is the act of it
Frames disbelief as an act, a person refusing to accept a specific report; it clusters around those who would not believe the news that Jesus had risen.Mrk 16:11Luk 24:11Luk 24:41
Reaches beyond doubting a fact to being unfaithful and breaking faith with God, not merely failing to be convinced.2Ti 2:13
Both
Both name the failure to trust God and can carry the darker note of unfaithfulness; Paul sets them side by side, using the verb of those who were unfaithful and the noun of their unbelief.Rom 3:3
Names the act of refusing to accept a report as true, above all the disciples disbelieving the news that Jesus was alive.Luk 24:11Mrk 16:11Luk 24:41Act 28:24
Carries a covenant sense of being unfaithful, breaking faith with God, set against the God who stays faithful even so.Rom 3:32Ti 2:13
Both
Both mark the absence of faith in God's message, the same fundamental non-response, whether named as an act of disbelief (the verb) or as a settled condition (the adjective).Mrk 16:162Co 4:4
Used as a noun for a whole class of people, the unbelievers, those outside the faith as a settled group: an unbelieving spouse, unbelievers in court, at a shared table, or in the assembly.1Co 7:122Co 6:141Ti 5:81Co 6:6
Describes faithlessness as a fixed quality or character, a faithless generation or a person urged to stop being faithless.Mat 17:17Jhn 20:27Tit 1:15
Can turn passive to mean unbelievable or incredible, said of a claim rather than of a person, a shade the verb never carries.Act 26:8
apisteō in the other biblical languages
אָמַןHebrew“be faithful”the Hebrew verb for believing and being faithful; Hebrew has no single word for its opposite and simply negates this one
A privative verb: it exists only to negate, naming the refusal or failure to believe as an event, something the positive Hebrew verb cannot express. The sharpest use is the disciples repeatedly disbelieving the reports that Jesus was alive, even disbelieving for joy when he stood before them.Mrk 16:11Luk 24:11Luk 24:41
Sorts an audience into two camps at a single hearing, the believers set against those who refuse, a division the word carries in itself.Act 28:241Pe 2:7
Both
Both verbs work the same twin concept, trusting a spoken word and being faithful in a bond, and they stand at opposite poles of it: the Greek word is the exact negation of what the Hebrew word affirms. On the believing side, Israel trusts the LORD while the disciples refuse to trust the resurrection news.Exo 4:31Luk 24:11
Both also reach past belief into faithfulness itself, one word for keeping faith and the other for breaking it: God establishes a faithful, lasting house, while breaking faith is what it means to be unfaithful, though even then God stays faithful.1Ki 8:262Ti 2:13Rom 3:3
The positive term: it can affirm trust outright, and it grounds Israel's foundational act of faith, counting a person as right with God for believing his promise.Gen 15:6Exo 14:312Ch 20:20
Denotes solid reliability and permanence with no Greek counterpart in this pairing: a sure and lasting house, a faithful priest, a prophet confirmed as trustworthy. This is the root behind "amen."2Sa 7:161Sa 2:351Sa 3:20
מָעַלHebrew“be unfaithful”the Hebrew verb for acting treacherously and breaking faith, close to this word's be-unfaithful sense
Names the inward act of refusing to accept a report as true, to disbelieve testimony one has heard; this is a failure of the mind to trust a message, and it dominates the word's use as the disciples reject the news that Jesus is alive.Mrk 16:11Luk 24:11Act 28:24
Reaches beyond a relationship of trust to unbelief toward the gospel itself, so that the one who will not believe stands condemned or stumbles over the rejected cornerstone.Mrk 16:161Pe 2:7
Both
Both describe God's own people proving unfaithful to him, breaking the trust of the covenant relationship; the Old Testament calls Israel's treachery against the LORD by the Hebrew word, and the New Testament describes some of Israel failing the trust of God's promises with the Greek word.Lev 26:40Dan 9:7Rom 3:32Ti 2:13
Names an outward deed of treachery against a sacred trust, seizing what is devoted to God or defiling the sanctuary, a betrayal carried out in action rather than a failure to believe.Jos 7:1Lev 5:152Ch 26:16
Extends to the betrayal of a marriage bond, the wife who breaks faith with her husband, a domain of concrete relational treachery that the Greek word never touches.Num 5:12Num 5:27
What scholars say about apisteō
ἀπιστέω is the privative compound of πιστεύω, and its range tracks the breadth of the πιστ- root, spanning cognitive non-belief and relational infidelity. BDAG distinguishes two senses: (1) to refuse to believe, disbelieve (Mk 16:11, 16; Lk 24:11, 41; Ac 28:24; 1 Pt 2:7), and (2) to be unfaithful, prove false (Ro 3:3;2 Ti 2:13), the latter set in antithesis to divine πίστις and πιστός. The classification of Romans 3:3 is discussed in the major commentaries: Cranfield and Dunn read ἠπίστησαν as "were unfaithful" on the strength of the πίστις τοῦ θεοῦ contrast, against a reading of simple disbelief. LSJ attests both the disbelieve and the prove-false values in classical usage.
Sources
BDAG, s.v. ἀπιστέωlexicon
LSJ, s.v. ἀπιστέωlexicon
H. Balz, EDNT, s.v. ἀπιστέωtheological-dictionary
C. E. B. Cranfield, Romans (ICC), on 3:3commentary
J. D. G. Dunn, Romans 1-8 (WBC 38A), on 3:3commentary