A dupe is a positive copy of a positive. A dupe can also be a negative copy of a negative. A dupe is a print made in the reversal process. It can sometimes be clearer to call something a dupe, because to simply say “positive print” you could just mean a positive copy of a negative, which would not be a dupe.
Glossary of Film Terms - http://homepage.newschool.edu/~schlemoj/film_courses/glossary_of_film_terms/
reprinted with permission