Actual definition of MVP from BBWAA site:
There seems to always be a debate about the definition of the MVP. What does the ballot say?
There is no clear-cut definition of what Most Valuable means. It is up to the individual voter to decide who was the Most Valuable Player in each league to his team. The MVP need not come from a division winner or other playoff qualifier.
The rules of the voting remain the same as they were written on the first ballot in 1931:
1. Actual value of a player to his team, that is, strength of offense and defense.
2. Number of games played.
3. General character, disposition, loyalty and effort.
4. Former winners are eligible.
5. Members of the committee may vote for more than one member of a team.
You are also urged to give serious consideration to all your selections, from 1 to 10. A 10th-place vote can influence the outcome of an election. You must fill in all 10 places on your ballot. Only regular-season performances are to be taken into consideration.
Keep in mind that all players are eligible for MVP, including pitchers and designated hitters.