Abbreviation: VC = "Vibration Compensation" (Tamron)

The abbreviations means "Vibration Compensation"

Explanation from Tamron

amronís Unique State-of-the-Art In-Lens Image Stabilization System
Handheld camera shake is the leading cause of blurry and unsharp pictures. Several leading companies now make lenses with built-in optical image-stabilization systems that sense the amplitude and direction of the shake and compensate by moving optical groups within the lens. Tamronís exclusive new Vibration Compensation (VC) system thatís built into the Tamron AF28-300mm F/3.5-6.3 XR Di VC LD Aspherical (IF) Macro and the Tamron AF18-270mm F/3.5-6.3 Di-II VC LD Aspherical (IF) Macro lenses performs a similar function, but it executes it much more effectively due to its innovative breakthrough design.

While other image-stabilization systems can only correct the effects of camera shake in horizontal or vertical planes, Tamronís VC system uses a tri-axial configuration that employs three pairs of driving coils and low-function ball bearings placed around the shake-compensating optical group to produce, in effect, a free-floating shake compensator. This simple, elegant system is able to compensate for camera shake that occurs in diagonal direction as well as for up-and-down and side-to-side movements. Furthermore, due to its simple, low-friction design it is more responsive and durable than previous systems. TheTamron 28-300mm VC and 18-270mm VC lenses incorporate a highly sensitive and accurate gyro sensor for detecting even the slightest hand shake, and that,combined with a 32-bit RISC CPU and Tamronís proprietary Algorithms and actuator, provides unequalled real-world performance. The bottom line: Tamron VC provides up to a 4-stop advantage in shooting sharp handheld pictures at slower shutter speeds along with a smooth, stable viewfinder image that is the envy of other shake-control systems. You can expect to see the VC feature built into more Tamron lenses in the future.

See examples of effected products

Tamron AF 28-300mm f/3,5-6,3 XR Di VC

See links

tamron-usa.com