Riprap

Part of speech: noun

Pronunciation: /ˈɹɪpɹap/

Definitions

1. A technique that involves using random stones to protect the edges of waterways and prevent soil loss from erosion
2. A covering of loose rocks placed to guard soil from erosion caused by water or weather
3. A bed of stones arranged to shield riverbanks or shorelines from being worn away

Etymology: Riprap is a reduplication of "rap", an old word meaning a blow or stroke, with the vowel changed from "a" to "i" to give the doubled form its rhythm. The pattern is the same one behind "zigzag" and "flip-flop," where a repeated syllable with a shifted vowel sounds like a repeated motion. The link to a blow is probably what gave the word its sense here: heaped stones were dumped or struck into place in quick succession to build a bank that could take the force of moving water. The word's core idea is therefore a pile of loose stones laid down in a sequence of rapid placements, not a single fixed structure. That is why the term is used for an unmortared mass of rock, dumped or set to shield a riverbank, shoreline, or bridge foundation from erosion. The stones are meant to absorb and scatter the energy of the current rather than resist it as a solid wall would.

Synonyms: rock fill, revetment