Of considerable weight (5)
(Other definitions for heavy that I've seen before include "Villain" , "Hard to lift" , "Difficult to lift" , "Not light" , "Weighty - ponderous" .)
(Other definitions for hefty that I've seen before include "Muscular" , "Large and beefy" , "Hulking" , "Sizeable" , "Brawny" .)