spark has 20 distinct synonyms spread across 6 of its 8 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.
merriment expressed by a brightness or gleam or animation of countenance
“he had a sparkle in his eye”
electrical conduction through a gas in an applied electric field
a small but noticeable trace of some quality that might become stronger
“a spark of interest”
Scottish writer of satirical novels (born in 1918)
a small fragment of a burning substance thrown out by burning material or by friction
Synonyms, antonyms and the broader and narrower relations for spark come from Princeton University’s WordNet. Full sources and licences.