Visual Basic Custom Control.A software module that can be used in many different applications.

Visual Basic Extension (file name extension)

n. Short for Visual Basic custom control. A software module that, when called by a Visual Basic application, produces a control that adds some desired feature to the application. A VBX is a separate executable file, usually written in C, that is dynamically linked to the application at run time and can be used by other applications, including some applications not developed in Visual Basic. Although VBX technology was developed by Microsoft, most VBXs have been written by third-party developers. VBXs are still in use, but the technology has been superseded by OCXs and ActiveX controls. See also control (definition 2), Visual Basic. Compare ActiveX controls, dynamic-link library, OCX.