The textbook for my Game Design subject is Rules of Play by Katie Salen & Eric Zimmerman.
In this post (and proably future posts) I am going to post some useful information from the book.
I think these two definitions of meaningful play are worth further consideration:
Meaningful play in a game emerges from the relatonship betwee player action and system outcome; it is the proces by which a player takes action within the designated system of a game and the system responds to the action. The meaning of an action in a game resides in the relationship between action and outcome. (descriptive definition)
Meaningful play occurs when the relationships between actions and outcomes in a game are both discernable and integrated into the larger context of the game. Creating meaningful play is the goal of successful game design. (evaluative definition)