That doesn't appear to be a system icon/notification that I'm familiar with. Guessing it's a third party app ... Have you recently installed any new apps?
Was it on the left or the right side of the status bar? If it appears on the left, then the next time you see it, swipe down the notification panel, where you should see more details associated with the icon.
I did download an exercise page that I obtained from a place called "Community Hospital". I used that app for a couple of days and then uninstalled it. It could be, and probably is, the reason for the strange icon (which appeared at the top LEFT of the screen).