• (n.) A subsoil made up of small stones or finely-broken rock; brash.
Stone'brash` noun A subsoil made up of small stones or finely-broken rock; brash. 
Stonebrash is a soil made of small stones or broken rock. The term originated for the subsoil of north-western Wiltshire which consisted of a reddish calcaerous loam mingled with flat stones.