From Longman Dictionary of Contemporary Englishhard rockˌhard ˈrock noun [uncountable] APMa type of rock music that is played loudly, has a strong beat, and uses electric instruments
Examples from the Corpus
hard rock• In an area with such rapid changes in temperature as to erode hard rock into sand, soft shells would not have survived.• It is very difficult dealing with fractures and dislocations which have happened on fairly hard rock climbs.• They still play honest hard rock, but now it sounds fresher and has thousands of hard edges.• Its overhanging walls provide a number of hard rock climbs. 