Ok, I am for sure stealing the use of coark for small-scale rocks (I even think I know were to get some of better than notice-board thickness, too).
Here in the States, "rip rap" is both a common term, but also a engineer-specified product. As a grading standard for natrually-occuring aggregate, it's material that is larger than "cobbles" (4-8") and smaller than "boulders" (>24"). It's also a waste product from the quarrying industry, and represents an excellent vehicle for handling their scrap bits.
This crops up in maritime/coastal projects. Rip rap is used for jetties and breakwaters, and for some forms of erosion control and seawall protection.
Also will crop up in beach preservation projects, especially on high-energy coast lines like the US NW. Corps of Engineers put out requests for "beach sand" for a project on the Oregon coast which called for well-graded sand of 10-12" size. (The NW US coast is tectonic, so there's not a uniform shallow slope up to the beach area, and it's exposed to high winds and storms. So, ordinary "sand" is less common (very much only found in protected inlets and bays and the like).
This is rather a stark contrast to the Texas coast, which is shallow-pitched, distinctly low-energy, and a windward shore. Excepting the occasional tropical storm and hurricane.