Jack West defines Open Theism:
An Open Theist is one who approaches God’s Word with an open mind. That’s not what the word “Open” stands for in “Open Theism,” but it does apply.
No, “Open” refers to the future. We believe that the future is completely open even to God. It is not decided, determined or exhaustively known. Although it is somewhat planned. God does make plans for the future and makes those plans known to us through prophesy. Our having approached God’s Word with an “open mind” is however how we came to believe that the future is “open.”
That is what I meant in the first paragraph, that we approach the Bible as if it accurately represents God. So we are open to anything it says that may contradict our preconceived ideas. When the Bible represents Him in a way that does contradict our own ideas we don’t try to make the passage fit into our ideas somehow. We don’t try to rationally explain, or just attribute it to metaphor, poetry or anthropomorphism.
For example when God says to Abraham “now I know,” we don’t say “really He meant ‘now you know,’ God already knew what Abraham would do.” The preconceived idea is that God already knows the future exhaustively, so for Him to say “now I know” contradicts that idea.
Instead of trying to explain away that representation to mold it to our idea of Him we have changed and molded our ideas to fit into that representation. We actually believe that God learned something at that (now) point.
If we started out believing that God never learns anything new and we read that He learned something, we altar our theology, not the meaning and teaching of the passage.