Lewis Short
substrāmen (noun N) : substerno
* What is strewn under, litter: molle,Varr. R. R. 3, 10, 4; 3, 6, 5; 3, 9, 8.
* Transf., supports: lubrica roboreis aderant substramina plaustris,i. e. rollers,Sil. 12, 444.
Charlton T. Lewis, Charles Short, A Latin Dictionary