weighty

And so a weighty rock she aimed / With much enthusiasm

To fund the purchase, he had to sell a late Renoir, The Judgment of Paris, with its depiction of weighty ladies frolicking in a roseate garden.

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 se…

a weighty argument