weighty

1. (figurative) Important; serious; not trivial or petty.Examples: "a weighty argument"; "But I have now reached a point in the progress of my narrative, when it becomes necessary to turn away from these light descriptions, to the more grave and weighty matter of the second battle with Master Tibeats, and the flight through the great Pacoudrie Swamp."Synonyms: grave, solemn, austere, demure, serious, grave, earnest, grievousfiguratively