Compounds having the structures RS2H, RS3H ... RSnH, in which Sn is a chain of sulfur atoms, and R is hydrocarbyl. Some people exclude hydrodisulfides from the class hydropolysulfides.
PAC, 1995, 67, 1307 (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1342