Riprap
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.
Illustration: Riprap
Photograph: Riprap
Source: The image above represents what the public sees relating to riprap.
TxDOT Visual Dictionary