Question:
What does corruptible and incorruptible mean?

Answer:
I believe that when the Bible talks about something being “corruptible” or “in corruption,” it is talking about things of this world which will pass away with this world. Conversely, when the Bible talks about things being “incorruptible,” it is talking about the things of God that will not pass away. In 1 Corinthians 9:25, Paul tells us how people of this world work to gain treasures that will pass away with this world, but the treasures that we lay up in heaven are incorruptible, and will never pass away.

Peter tells us in 2 Peter 1:4 how we have escaped the corruption of this world, and have gained an incorruptible inheritance (1 Peter 1:4) that is reserved for us in heaven.

You also ask about carnal believers. This past semester at college, I had the “privilege” of living with someone that I considered to be somewhat of a carnal believer.
Carnal believers are people who have been saved, but you could never tell it by their daily walk. When I think about carnal believers, I always think of 1 Corinthians 3:10-15. This passage speaks very clearly to me about people who are saved but do not walk as Christ would have us walk.
I said that I thought one of my former roommates was “somewhat” of a carnal believer. (I don’t know for sure if he had accepted Christ into his heart, but he said that he had so I assumed that he had.) What I meant by “somewhat” of a carnal believer was that while he sometimes acted in a “Christ-like manner,” he seemed to love the world more than he loved Jesus.
We must be careful how we deal with these people. We can’t condemn them because of their sin, for we all sin. Jesus said, “He that is without sin among you, let him…cast a stone” (John 8:7).
Trying to set a positive example through my life and praying for these people is about the best ministry that I can think of.