http://lmgtfy.com/?q=mind+definition
Well, you only referred to the brain. There is a difference between brain and mind.
Basically, the brain is the organ of the body in the head that controls functions, movements, sensations, and thoughts and ability to think and reason.
The mind thinks, reasons, feels and remembers.
Then there is consciousness which is the mind and thoughts.
Mind vs brain has been debated for centuries in philosophy, especially when it comes to consciousness and unconsciousness.
Examples are this thread and on quora:
https://www.quora.com/topic/Brain-vs-the-Mind