Sin is described in the Bible as transgression of the law of God and rebellion against God.
Romans 14:23
23. And he that doubteth is damned if he eat, because he eateth not of faith: for whatsoever is not of faith is sin.
Galatians 5:19-21
19. Now the works of the flesh are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness,
20. Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies,
21.envy, murders, drunkenness, revelries, and the like; of which I tell you beforehand, just as I also told you in time past, that those who practice such things will not inherit the kingdom of God.
James 4:17
17. Therefore to him that knoweth to do good, and doeth it not, to him it is sin.
1 John 3:4
4. Whosoever committeth sin transgresseth also the law: for sin is the transgression of the law.