WordNet records no synonym and no antonym for paragraph. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
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.
divide into paragraphs, as of text
“This story is well paragraphed”
write about in a paragraph
“All her friends were paragraphed in last Monday's paper”
write paragraphs; work as a paragrapher
one of several distinct subdivisions of a text intended to separate ideas; the beginning is usually marked by a new indented line
Synonyms, antonyms and the broader and narrower relations for paragraph come from Princeton University’s WordNet. Full sources and licences.