post has 22 distinct synonyms spread across 15 of its 23 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.
assign to a post; put into a post
“The newspaper posted him in Timbuktu”
display, as of records in sports games
ride Western style and bob up and down in the saddle in rhythm with a horse's trotting gait
the position where someone (as a guard or sentry) stands or is assigned to stand
“a soldier manned the entrance post”
military installation at which a body of troops is stationed
“this military post provides an important source of income for the town nearby”
a job in an organization
“he occupied a post in the treasury”
an upright consisting of a piece of timber or metal fixed firmly in an upright position
“he set a row of posts in the ground and strung barbwire between them”
United States aviator who in 1933 made the first solo flight around the world (1899-1935)
United States female author who wrote a book and a syndicated newspaper column on etiquette (1872-1960)
United States manufacturer of breakfast cereals and Postum (1854-1914)
any particular collection of letters or packages that is delivered
“your mail is on the table”
a pole or stake set up to mark something (as the start or end of a race track)
“a pair of posts marked the goal”
the system whereby messages are transmitted via the post office
“the mail handles billions of items every day”
the delivery and collection of letters and packages
“it came by the first post”
Synonyms, antonyms and the broader and narrower relations for post come from Princeton University’s WordNet. Full sources and licences.