In Revelation 1:10, John said that he was in the "Spirit" what did he mean?
"I was in the Spirit on the Lord's day, and heard behind me a great voice, as of a trumpet,"
It means that while he was physically on Patmos, his spirit was elsewhere. A similar thing happened to Ezekiel several times when God took him to Jerusalem to see the sinful things happening there.
"He stretched out the form of a hand, and took me by a lock of my hair; and the Spirit lifted me up between earth and heaven, and brought me in visions of God to Jerusalem, to the door of the north gate of the inner court, where the seat of the image of jealousy was, which provokes to jealousy" (Ezekiel 8:13).
"In the twenty-fifth year of our captivity, at the beginning of the year, on the tenth day of the month, in the fourteenth year after the city was captured, on the very same day the hand of the LORD was upon me; and He took me there. In the visions of God He took me into the land of Israel and set me on a very high mountain; on it toward the south was something like the structure of a city" (Ezekiel 40:1-2).
Paul mentions it as well:
"It is doubtless not profitable for me to boast. I will come to visions and revelations of the Lord: I know a man in Christ who fourteen years ago -- whether in the body I do not know, or whether out of the body I do not know, God knows -- such a one was caught up to the third heaven. And I know such a man -- whether in the body or out of the body I do not know, God knows -- how he was caught up into Paradise and heard inexpressible words, which it is not lawful for a man to utter" (II Corinthians 12:1-4).