indent has 4 distinct synonyms spread across 3 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.
set in from the margin
“Indent the paragraphs of a letter”
cut or tear along an irregular line so that the parts can later be matched for authentication
“indent the documents”
an order for goods to be exported or imported
the space left between the margin and the start of an indented line
Synonyms, antonyms and the broader and narrower relations for indent come from Princeton University’s WordNet. Full sources and licences.