organization has 10 distinct synonyms spread across 7 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 group of people who work together
an organized structure for arranging or classifying
“he changed the arrangement of the topics”
the persons (or committees or departments etc.) who make up a body for the purpose of administering something
“he claims that the present administration is corrupt”
the act of organizing a business or an activity related to a business
“he was brought in to supervise the organization of a new department”
an ordered manner; orderliness by virtue of being methodical and well organized
“his compulsive organization was not an endearing quality”
the activity or result of distributing or disposing persons or things properly or methodically
“his organization of the work force was very efficient”
the act of forming or establishing something
“the constitution of a PTA group last year”
Synonyms, antonyms and the broader and narrower relations for organization come from Princeton University’s WordNet. Full sources and licences.