.MDIMPORTER File Extension
What is an MDIMPORTER file?
Data plugin file created for the Spotlight search tool; returns metadata contained with a file to the Spotlight tool so file data can be searched and retrieved; not meant to be opened manually.
When a file is changed, Spotlight loads the specific MDIMPORTER file and extracts the metadata.
To see what MDIMPORTER files you have installed go to the Spotlight folder located in the /System/Library/ directory on your Macintosh HD.
NOTE: If a file does not have a MDIMPORTER, it will only be able to be searched for by the file name.