Riprap is rock or other material placed to reinforce shorelines, streambeds, bridge abutments, pilings and other structures against water, wave or ice erosion. Common riprap materials are granite and modular concrete blocks. Riprap is also know as rip raph, rap-rap, shot rock, rock armor and rubble.

Riprap illustration

Illustration: Riprap


Riprap photo

Photograph: Riprap

Source: The image above represents what the public sees relating to riprap.