Alluvium \Al*lu"vi*um\, n.; pl. E. {Alluviums}, L. {Alluvia}. [L., neut. of alluvius. See {Alluvious}.] (Geol.) Deposits of earth, sand, gravel, and other transported matter, made by rivers, floods, or other causes, upon land not permanently submerged beneath the waters of lakes or seas. --Lyell.