president has 8 distinct synonyms spread across 4 of its 6 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.
an executive officer of a firm or corporation
the person who holds the office of head of state of the United States government
“the President likes to jog every morning”
the chief executive of a republic
the officer who presides at the meetings of an organization
“address your remarks to the chairperson”
the head administrative officer of a college or university
the office of the United States head of state
“a President is elected every four years”
Synonyms, antonyms and the broader and narrower relations for president come from Princeton University’s WordNet. Full sources and licences.