Definition of Riss in US English:

Riss

noun

Geology
  • 1usually as modifier The penultimate Pleistocene glaciation in the Alps, possibly corresponding to the Saale of northern Europe.

    • ‘Gunz, Mindel, Riss and Wurm are the names of four ice ages.’
    1. 1.1 The system of deposits laid down during the Riss glaciation.

Origin

Early 20th century: from the name of a tributary of the Danube River in Germany.

Pronunciation

Riss

/ris/