I. ˈrip-ˌrap noun
Etymology: obsolete riprap sound of rapping
Date: 1833
1. : a foundation or sustaining wall of stones or chunks of concrete thrown together without order (as in deep water) ; also : a layer of this or similar material on an embankment slope to prevent erosion
2. : material used for riprap
II. transitive verb
Date: 1848
1. : to form a riprap in or upon
2. : to strengthen or support with a riprap