I think it is how many people have viewed that particular post.
I went back to look at something I had posted. It seems that the original poster (me) has the most views and it gets progressively lower as it goes on.
At first I thought it was how many times that member had looked at the topic, but I don't think that is the case because in one of the topics I started, it says 187 views by me and I'm pretty sure I didn't view the topic 187 times. It is more likely that it was viewed a total of 187 times by everyone combined.