Entry 1 sense Webster, 1913 Folder /fōl'-dẽr/ · Fold·er · IPA /ˈfoʊɫdɚ/ 01 n. One who, or that which, folds; esp., a flat, knifelike instrument used for folding paper. 1. One who, or that which, folds; esp., a flat, knifelike instrument used for folding paper.