col·lu·vi·um 
(kə-lvē-əm)
(kə-lvē-əm)n. pl. col·lu·vi·ums or col·lu·vi·a (-vē-ə)
A loose deposit of rock debris accumulated through the action of gravity at the base of a cliff or slope.
[Latin, a collection of washings, dregs, from colluere, to wash thoroughly : com-, intensive pref.; see COM- + -luere, to wash; see leu(ə)- in the Appendix of Indo-European roots.]
col·luvi·al adj.