Scriptural reference to explain what the word "gospel" means? Would someone explain what the word gospel means and give a biblical reference which contains the word?
The definition of the Greek word euangelizō is "good news." (Koiné Greek is the original language of the New Testament.) A familiar verse with euangelizō in it is Luke 2:10, which reads, 


  But the angel said [to the shepherds], "Do not be afraid; for behold, I bring you good news [i.e., euangelizō] of great joy which will be for all the people; for today in the city of David there has been born for you a Savior, who is Christ the Lord" (including v.11).


Interestingly, an evangelist, a person who is empowered by the Holy Spirit of God and then given to the church, is one who is gifted to spread the glad tidings that Jesus is both Savior and Lord (see Ephesians 4:11-12). 

Evangelists are like obstetricians (so-called "baby doctors") who are gifted by God to help bring spiritual newborns into the kingdom of Jesus Christ and his universal church. When evangelists preach the good news, people get saved by believing on and receiving Jesus into their lives as their rescuer and boss. 

I encourage you to use a concordance to look up the word news, which appears numerous times in the New Testament (at least 43 times in the New International Version of the Bible) in order to get a well-rounded view of what the gospel of Jesus Christ is.