1. slang A newly commissioned officer in the US Army, Air Force, or Marine Corps, especially a second lieutenant. Derived from the practice of shaving the tail of untrained pack animals. It was the shavetail's first mission, and he realized he was in over his head. They court-martialed the shavetail for disobeying the admiral's orders.

2. slang By extension, any person who is inexperienced in a given field, industry, profession, etc. Why don't you give the case to the shavetail we just hired? It will be tough, but it will put her abilities to the test. some of the older employees resented the fact that a shavetail like me was promoted through the ranks of the company so quickly.