The Collaborative International Dictionary of English v.0.48:

Flysch \Flysch\ (fl[=e]sh), n. [A Swiss word, fr. G. fliessen to
   flow, melt.] (Geol.)
   A name given to the series of sandstones and schists
   overlying the true nummulitic formation in the Alps, and
   included in the Eocene Tertiary.
   [1913 Webster]