A reduction print is a print of a large-size format film converted to a smaller size format (for example, a 70mm print converted to 35mm). Often this is necessary because not all theatres have a screen of the size required to show a film in large format, or indeed the projection equipment. This is especially true of some screens in multiplex theatres. In former days, it was true of the neighbourhood theatres located outside of downtown areas.
Conversely, a "blow-up print" is a regular format film converted to larger size (i.e., 35mm to 70mm). This was once often done so that "regular-sized" film would seem even more impressive on screens such as the ones in Cinerama theatres.