Superlative form of weighty: most weighty.(adjective)
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Use "weightiest" in a sentence
"He had a peculiar way of prefacing his weightiest sentences with a short word, uttered twice in a guttural manner, clearing up his throat, or his "gullick," as he would term it, just before uttering them."
"One of the weightiest is the unexpected mea culpa that Abby Mann wrote for the defendant Dr. Janning, played by Burt Lancaster, in "Judgment at Nuremberg.""
"Among these the weightiest was the silent George Washington."