1. ponderous, massive, weighty. 5. dense. 9. onerous, grievous, cumbersome; difficult, severe. 14. Heavy, momentous, weighty refer to anything having a considerable amount of figurative weight. Heavy suggests the carrying of a figurative burden: words heavy with menace. Momentous emphasizes the idea of great and usually serious consequences: a momentous occasion, statement. Weighty, seldom used literally, refers to something heavy with importance, often concerned with public affairs, which may require deliberation and careful judgment: a weighty matter, problem. 15. gloomy, mournful, dejected, despondent, downcast, downhearted. 16. tedious, tiresome, wearisome, burdensome, boring. 17. sluggish, lumbering. 19. lowering, gloomy.