(a)heavyunusually great in degree or quantity or number“heavy taxes”, “a heavy fine”, “heavy casualties”, “heavy losses”, “heavy rain”, “heavy traffic”
(a)heavyof the military or industry; using (or being) the heaviest and most powerful armaments or weapons or equipment“heavy artillery”, “heavy infantry”, “a heavy cruiser”, “heavy guns”, “heavy industry involves large-scale production of basic products (such as steel) used by other industries”
(a)heavymarked by great psychological weight; weighted down especially with sadness or troubles or weariness“a heavy heart”, “a heavy schedule”, “heavy news”, “a heavy silence”, “heavy eyelids”
(s)dense, heavy, impenetrablepermitting little if any light to pass through because of denseness of matter“dense smoke”, “heavy fog”, “impenetrable gloom”
(s)grave, grievous, heavy, weightyof great gravity or crucial import; requiring serious thought“grave responsibilities”, “faced a grave decision in a time of crisis”, “a grievous fault”, “heavy matters of state”, “the weighty matters to be discussed at the peace conference”
(s)heavy, lumbering, ponderousslow and laborious because of weight“the heavy tread of tired troops”, “moved with a lumbering sag-bellied trot”, “ponderous prehistoric beasts”, “a ponderous yawn”
(s)arduous, backbreaking, grueling, gruelling, hard, heavy, laborious, operose, punishing, toilsomecharacterized by effort to the point of exhaustion; especially physical effort“worked their arduous way up the mining valley”, “a grueling campaign”, “hard labor”, “heavy work”, “heavy going”, “spent many laborious hours on the project”, “set a punishing pace”