metafile - technical definition

A file that contains other files. It generally refers to graphics files that can hold vector drawings and bitmaps. For example, Windows Metafiles (WMFs) and Enhanced Metafiles (EMFs) can store pictures in vector graphics and bitmap formats as well as text. A Computer Graphics Metafile (CGM) also stores both types of graphics. See Windows Metafile and CGM.

Container Formats
Typically called a "container format," different audio and video streams residing in one file is another type of metafile. AVI and MPEG formats are examples. See AVI and MP4.