skeleton has 7 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.
something reduced to its minimal form
“the battalion was a mere skeleton of its former self”
a scandal that is kept secret
“there must be a skeleton somewhere in that family's closet”
the hard structure (bones and cartilages) that provides a frame for the body of an animal
the internal supporting structure that gives an artifact its shape
“the building has a steel skeleton”
Synonyms, antonyms and the broader and narrower relations for skeleton come from Princeton University’s WordNet. Full sources and licences.