I was reading a book and it said that internal/intrinsic growth is defining property of life and not extrinsic growth as saying accumulation of dust on a book makes it a bit bigger, even if it is by a few mm but since it's just a deposition of material and it can be removed, so it's not living. Now, if we see intrinsic growth then I had a doubt. Say we took a piece of log and dipped it into the water. Then the log will also grow in size and this growth is from inside, but the log of wood isn't living. So, I was in doubt that how can I define growth for a living.
If you are just asking what does growth mean in the context of living systems then it almost always means replication of a unit: cell or genetic material (cell division, DNA replication etc).
Note that increase in cell volume or the inter-cellular space (accretionary growth) also happen in living systems and they are also considered growth. However, at a gross level these processes are indistinguishable from what is happening to wood that is dipped in water.
So growing is not an exclusive feature of living systems but still one of the defining features.