Featherlight is an adjective that describes something that is very light, almost weightless. If we were to look for antonyms or opposite words for featherlight, we would search for words that imply heaviness, density, or mass. Some suitable antonyms for featherlight could be heavy, bulky, solid, substantial, weighty, dense, and ponderous. These words describe objects or materials that are considerably weightier or denser than something that is featherlight. For instance, a boulder could be heavy, whereas a feather is featherlight. By considering such antonyms, we can better understand the meaning and usage of the word featherlight in different contexts.