ponderous

1. (figuratively, by extension) Serious, onerous, oppressive.Examples: "It was Dryden's opinion . . . that the drama required an alternation of comick and tragick scenes; and that it is necessary to mitigate, by alleviations of merriment, the pressure of ponderous events, and the fatigue of toilsome passions."; "In its court-yard—worthy of the Castle of Otranto in its ponderous gloom—is a massive staircase."; "For the time, her own body was the source of all the life in the world, which tried to burst forth here—there—and was repressed now by Mr. Bax, now by Evelyn, now by the imposition of ponderous stupidity."Synonyms: oppressive, seriousbroadlyfiguratively

2. (rare) Characterized by or associated with pondering.Examples: "Ponderous thoughts take hold of the heart; musing maketh the fire to burn, and steady sight hath the greatest influence upon us."; "The acute and ponderous mind of Dr. Johnson was not always right in its decisions."; "They are the pleasantest of all companions, and perhaps the most affluent in correct opinions of men and things generally, although little addicted to ponderous consideration or deep research."rare

3. (obsolete) Dense.obsolete