1. It is entirely possible that you are not really 10% body fat. Depending on how I measure mine I can be anywhere from 13% to 19%. Revisit your measuring methods.
Try a cutting cycle and see what happens to your muscle definition.
2. No specific exercise will do anything for muscle definition. This is basically BS.
3.
http://www.t-nation.com/ALSAuthor.do?p= ... u&pageNo=1
Mirror Training
by Christian Thibaudeau
When your goal is to get very lean and dense, including a weekly posing session lasting 30 to 45 minutes can really make a difference in your appearance. Hold each of the mandatory bodybuilding poses (there's seven of them, eight if you count the "most muscular") for sixty seconds and repeat the cycle two or three times. Concentrate on maximally contracting the muscles. Muscle control really is improved through posing and so is muscle tonus, thus you'll look denser and more muscular, plus it'll actually help you with your lifting performance!
Heavy and Hard
by Christian Thibaudeau
Heavy lifting increases myogenic tone (tonus) which makes your muscles appear and feel "harder." Take two guys who have around the same amount of muscle mass and body fat; one is using heavy weights while the other one is using "pumping" techniques. Despite similar body composition, the heavy weight lifter will always look harder and denser while at rest. The pumper will look great when fully pumped up, but will quickly deflate once he exits the gym. So if you want a permanent muscular look, not a transient one, include some heavy lifting in your program!