That is how most folks refer to it. But it's also called a bump, a pucker, etc. What it is, is too much length at the upper back. [see the tutorial]. Its caused by those who have an erect posture. Or it can also be caused by those with average posture who carry their head and neck in an erect position. The alteration is called shortening the back: excess cloth is removed at the top of the back as shown by the dotted lines. The operation involves moving the collar and changing the shoulder seams. This covers most minor cases. Major cases call for major heroics, a later thread.