"Notched" describes something that has a small V-shaped or U-shaped cut in its edge. You might see a notched leaf (with little cuts along the edge), a notched belt (with holes cut in a row), or a notched stick used to keep count of something, like an old-fashioned tally. It's also used a bit loosely, like "she notched up another win" - meaning she added one more win to her record, as if cutting one more mark into a stick to count it.