What is the meaning of soul? This question is simple, but cannot be answered in just one line.
There are different stages of soul realisation.
The first stage in soul realisation involves the intellectual understanding that you are the soul, a spiritual being of diving intelligence, love and power. You are not the physical body, not the thoughts nor the emotions and not even the mind. The thoughts and emotions are products of the soul, just as the carpenter is not the furniture. The mind is just a subtle instrument of the soul, just as the computer is your instrument.
The second stage is experiencing one’s self as the soul during meditation, The person may experience not being able to feel the physical body, as though it has disappeared. The person may have an out of body experience, the soul occupying and manifesting in other subtle bodies of light and being able to travel at a speed faster than the speed of light. With further development, the person may have an experimental realisation of the nature of the soul.
The third stage in soul realisation is the experience of the incarnated soul (that is you) having union with the higher soul and realising that there is no separation between you and your higher soul. This incarnated soul and higher soul are actually one. The yogi also experiences oneness with other souls, not just humans souls, but all other types of souls. At this level, the process of realisation starts.
Reference : Achieving Oneness with the Higher Soul, Master Choa Kok Sui