n English physicist and electrical engineer who helped develop telegraphic and telephonic communications; in 1902 (independent of A. E. Kennelly) he suggested the existence of an atmospheric layer that reflects radio waves back to earth (1850-1925)
n a metal of relatively high density (specific gravity greater than about 5) or of high relative atomic weight (especially one that is poisonous like mercury or lead)
n loud and harsh sounding rock music with a strong beat; lyrics usually involve violent or fantastic imagery