asphalt has 1 distinct synonym spread across 1 of its 3 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
mixed asphalt and crushed gravel or sand; used especially for paving but also for roofing
a dark bituminous substance found in natural beds and as residue from petroleum distillation; consists mainly of hydrocarbons
cover with tar or asphalt
“asphalt the driveway”
Synonyms, antonyms and the broader and narrower relations for asphalt come from Princeton University’s WordNet. Full sources and licences.