What is dmsm?

DMSM is Defence Meritorious Service Medal, the third highest peacetime award, which is awarded to members of the U.S. Armed Forces for distinguished or unusual non-combat service.

But since you asked this question in a Health category, I suspect that you may be asking about DSM, which is Diagnostic and Statistical Manual of Mental Disorders.

Read more about the manual at http://allpsych.com/disorders/dsm.html