weighty

Having a lot of weight; heavy.

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.

Important; serious; not trivial or petty.

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.

Rigorous; severe; afflictive.