Yep, that is an erection. I have seen one before and that is one. A very hard and very nice one. I bet you know how to handle it. Take it rub it and let it down before you pass out from lack of blood to the brain---your other brain, that is.
After showing this photo to my fucking horny wife, she said that she would assume the position for you any time that you wanted to ride her. She put this photo in her favorite cocks collection. Our favorites section is her collection.