slick has 26 distinct synonyms spread across 8 of its 11 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.
a slippery smoothness
“he could feel the slickness of the tiller”
a magazine printed on good quality paper
1 of the 11 recorded senses carries no synonym, antonym or related term, so it is not shown above. Every sense, with its definition and examples, is on the full entry for slick.
Synonyms, antonyms and the broader and narrower relations for slick come from Princeton University’s WordNet. Full sources and licences.
a trowel used to make a surface slick