I know your deeds, that you are neither cold nor hot. I wish you were either one or the other! So, because you are lukewarm–neither hot nor cold–I am about to spit you out of My mouth.
The Laodiceans understood lukewarm. And, they understand that it was yucky to the taste. You see, outside of Laodicea was a spring where the city received its water. At the spring, the water was cool and refreshing. But, the water was moved to the city through an open viaduct and in the warm daytime sun it became lukewarm and almost too gross to drink. If you have ever come in from a hot Oklahoma summer day and taken a drink of water straight from the tap, you know how gross that lukewarm water tastes. This is what the Laodiceans faced everyday.
So, when Jesus talked about their faith being lukewarm, the Laodiceans knew how disgusted He was. Those who have a lukewarm faith are almost more dangerous to the Christian cause than those who are Christian-haters. You see, those who are lukewarm give mixed signals as to how a Christian should act and to whom a Christian should serve. In our modern day terms, we may refer to these people as Sunday-only Christians. Those who proclaim Christ in a big way on Sunday, but the rest of the week pursue a personal agenda away from Christ.