RO,
SKU ??? Oh talos wat is that ??
This is a generic term used by inventory planners. I guess you must have overlooked the entries in the SAP glossary when you were searching for the definition......
http://help.sap.com/searchbox#query=sku&startindex=1&filter=scm_a_resourceType(scm_v_resType311)
For a generic definition, you might consider the one offered by Wikipedia.
https://en.wikipedia.org/wiki/Stock_keeping_unit
Best Regards,
DB49