object has 4 distinct synonyms spread across 2 of its 7 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 tangible and visible entity; an entity that can cast a shadow
“it was full of rackets, balls and other objects”
(grammar) a constituent that is acted upon
“the object of the verb”
the focus of cognitions or feelings
“objects of thought”
(computing) a discrete item that provides a description of virtually anything known to a computer
“in object-oriented programming, objects include data and define its status, its methods of operation and how it interacts with other objects”
express or raise an objection or protest or criticism or express dissent
“She never objected to the amount of work her boss charged her with”
be averse to or express disapproval of
“My wife objects to modern furniture”
Synonyms, antonyms and the broader and narrower relations for object come from Princeton University’s WordNet. Full sources and licences.