"SAM" has many definitions depending on the field. Here are the most common ones:
SAM - Common Definitions
Military
Surface-to-Air Missile - a missile launched from the ground (or a ship) to intercept and destroy aircraft or other aerial targets
Business / Marketing
Serviceable Available Market - the portion of the Total Addressable Market (TAM) that a company can realistically target with its products or services. Used in the TAM-SAM-SOM framework for market sizing.
Software Asset Management - the practice of managing, controlling, and optimizing software licenses within an organization