rock borer
rock borer
n
(Animals) any of various sea creatures that bore into rock, such as some sea urchins, sponges, annelid worms, barnacles, isopods, and molluscs
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014