hammer drill
noun
a rock drill operated by compressed air in which the boring bit is not attached to the reciprocating piston
an electric hand drill providing hammering in addition to rotating action
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012