Not sure if my answer is unorthodox or not. But to me, faith is holding a belief in something while acknowledging that it may or may not be true... and being okay with that.
I will use an illustration. Faith is knowing (believing) that when I flip a light switch, the light will actually come on. It's happened before so I have confidence it will happen again. It's also, in the same way, knowing (believing) that when I talk to God in prayer, He actually hears me and has the power and willingness to answer me, in the way and at the time that He knows is best for me. I know this is true becuse He has done so for me in the past. So in a spiritual sense, faith is the confidence I have in Him, based on the relationship I have with Him.