The operative verb here is ἀρνέομαι (arneomai) which occurs 33 times in the NT. BDAG lists four basic meanings of this word, of which the third is relevant here, namely:
(3) to disclaim association with a person or event, deny,
repudiate, disown (verbally or nonverbally)
Within this meaning, BDAG goes on to list seven sub-meanings classified by what or who is being repudiated. Of these the second is relevant - of repudiating Christ in which several references are listed as follows:
- Matt 10:33 - But whoever denies Me before men, I will also deny him before My Father in heaven.
- Luke 12:9 - But whoever denies Me before men will be denied before the angels of God.
- Acts 3:13, 14 - The God of Abraham, Isaac, and Jacob, the God of our fathers, has glorified His servant Jesus. You handed Him over and rejected Him before Pilate, even though he had decided to release Him. You rejected the Holy and Righteous One and asked that a murderer be released to you.
- Jude 4 - For certain men have crept in among you unnoticed—ungodly ones who were designated long ago for condemnation. They turn the grace of our God into a license for immorality, and they deny our only Master and Lord, Jesus Christ.
- 2 Peter 2:1 - But false prophets also arose among the people, just as there will be false teachers among you, who will secretly bring in destructive heresies, even denying the Master who bought them, bringing upon themselves swift destruction.
- 1 John 2:23 - Whoever denies the Son does not have the Father, but whoever confesses the Son has the Father as well.
Then there is the group of texts, in all four Gospels discussing the incident when Peter denied knowing Jesus in Matt 26:70, 72, Mark 14:68, 70, Luke 22:57, John 13:38, 18:25, 27.
Note the consistent pattern here - people who actually knew who Christ was, denied knowing Him, or, refused to affirm or confess that Jesus is Lord and Savior.
[Important note - A person cannot deny Christ if the person does not know Christ in the first place.]
From the above pattern, we may summarize the act of "denying Christ" as either:
- Denying the we know Christ when we actually do (as did Peter), or,
- Denying Jesus' status and position as Lord and Savior, as taught in the Scripture
According to Jesus (Matt 10:33), denying Him as Christ is equivalent to denying the only means of salvation available to men (Acts 4:12); thus, if a person denies Jesus, that person has refused their salvation.
[Second Important Note: Peter denied his Lord, but was later forgiven when Peter confessed.]
John also summarized the situation this way in 1 John 5:11, 12 -
And this is that testimony: God has given us eternal life, and this
life is in His Son. Whoever has the Son has life; whoever does not
have the Son of God does not have life.