Preferably a short one. 'Description' fits my purpose very well, but is longer than I'd like (3 - 5 letters are ideal).
It's going to be used as a heading, umbrella-term, button or similar for image-metadata of some of the ones in Dublin Core; subject ("husband and children") and description ("family in front of waterfall"). And also tags ('Ben', 'Jeremy', 'Sarah', 'waterfall', 'holiday', 'Iceland')
Recognisable acronyms and abbreviations would also work, but usability goes first, so if nothing better is found, 'description' it is.
Edit: Clarification: 'Description' (as it is called for now) is the name of only one category in a software program for image-metadata. Other categories are 'Cam' (camera; shutterspeed, ISO, aperture etc.), 'GPS'/'Geo' (longitude, latitude) etc.