According to the Holman Illustrated Bible Dictionary,
“Rapture: God’s taking the church out of the world instantaneously.”
Rapture comes from the root word, rap: to snatch, and is closely related to rapt: snatched away; transported. The word rapture is not in the Bible, but the definition is certainly fulfilled in the following Scriptures:
1 Thessalonians 4:14-17
14For if we believe that Jesus died and rose again, even so God will bring with Him those who sleep [those who have died in belief] in Jesus. 15For this we say to you by the word of the Lord, that we who are alive and remain until the coming of the Lord will by no means precede those who are asleep [have died]. 16For the Lord Himself will descend from heaven with a shout, with the voice of an archangel, and with the trumpet of God. And the dead in Christ will rise first. 17Then we who are alive and remain shall be caught up together with them in the clouds to meet the Lord in the air. And thus we shall always be with the Lord.
“I will come again and receive you to Myself; that where I am, there you may be also.”
1 Corinthians 15:52
In a moment, in the twinkling of an eye, at the last trumpet [of the Church Age]. For the trumpet will sound, and the dead will be raised incorruptible [not to die again], and we shall be changed.
After these things [the last messages to all the churches] I looked, and behold, a door standing open in heaven. And the first voice which I heard was like a trumpet speaking with me, saying, “Come up here, and I will show you things which must take place after this.”