substramen
/sʌbˈstreɪmən/ /sʌbˈstrɑːmən/Geology. Now historical and rare
noun
The groundmass or matrix of a concretionary rock.
Origin
Late 18th century. From classical Latin substrāmen bedding for animals, litter, materials laid down on rough ground to provide a smooth surface for vehicles from substernere + -men; compare strāmen straw.