pinwheel has 3 distinct synonyms spread across 3 of its 4 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.
perennial subshrub of Tenerife having leaves in rosettes resembling pinwheels
a wheel that has numerous pins that are set at right angles to its rim
“he spun the pinwheel and it stopped with the pointer on `Go'”
a toy consisting of vanes of colored paper or plastic that is pinned to a stick and spins when it is pointed into the wind
a circular firework that spins round and round emitting colored fire
Synonyms, antonyms and the broader and narrower relations for pinwheel come from Princeton University’s WordNet. Full sources and licences.