Firstly, it means consecration or dedication unto God or holy uses. Secondly, Sanctification is a definite Christian experience whereby a believer's heart is circumcised, cleansed or purified of sinful nature, otherwise called inbred sin, adamic nature, the old man, the inward corruption. The believer by sanctification is rendered increasingly holy and is enabled to serve God without blemish in Holiness and Righteousness;
Some scripture to Consider!
Ephesians 5:25-27; 1Thessalonians 4:3-8; 5:22-24; Psalm 51:5-10; Hebrews 13:12,13,20,21; Acts 26:18.
Holiness is possible:
Luke 1:74-75. "That He would grant unto us, that we, being delivered out of the hand of our enemies, might serve Him without fear, In Holiness and Righteousness before Him, all the days of our life." 1 Peter 1:14-16. "As obedient children, not fashioning yourselves according to the former lusts in your ignorance: But as He which hath called you is holy, so be ye holy in all manner of conversation; Because it is written, Be ye holy; for I am holy." 2 Corinthians 5:17.
"Therefore if any man be in Christ, he is a new creature: old things are passed away; behold, all things are become new." 1 John 3:9. "Whosoever is born of God doth not commit sin; for his seed remaineth in him: and he cannot sin, because he is born of God."