A better definition is … Man’s effort to prove his worth to God.
Look what the Scripture says about religion:
Acts 26:5 Which knew me from the beginning, if they would testify, that after the most straitest sect of our religion I lived a Pharisee.
Galatians 1:13-14 For ye have heard of my conversation in time past in the Jews’ religion, how that beyond measure I persecuted the church of God, and wasted it: And profited in the Jews’ religion above many my equals in mine own nation, being more exceedingly zealous of the traditions of my fathers.
James 1:26-27 If any man among you seem to be religious, and bridleth not his tongue, but deceiveth his own heart, this man’s religion is vain. Pure religion and undefiled before God and the Father is this, To visit the fatherless and widows in their affliction, and to keep himself unspotted from the world.
Salvation is the belief in the death, burial and resurrection of the Lord Jesus, and confessing Him as God.
1 Corinthians 5:1-4 Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand; By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain. For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures; And that he was buried, and that he rose again the third day according to the scriptures:
Romans 10:9 That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved.
Also see What Religion?