1. JM generally refers to a legal master. It is one of the professional master's degrees in China, which has been offered since 1996 according to the Provisions on the Establishment of Professional Master's Degree Systems approved by the State Council. 2. JM stands for medium size in Japan, JL for large size, and Jo for extra large size. There are also other sizes such as JSS, JS, JM, JL, and Jo. These are Japanese sizes. Japanese size O is equal to L in Chinese, and size XXO is equal to XL. 3. JM can also mean "sister" in Chinese.