introversion has 3 distinct synonyms spread across 2 of its 3 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. Its 2 recorded opposites are ambiversion, extraversion.
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.
the folding in of an outer layer so as to form a pocket in the surface
“the invagination of the blastula”
Synonyms, antonyms and the broader and narrower relations for introversion come from Princeton University’s WordNet. Full sources and licences.
(psychology) an introverted disposition; concern with one's own thoughts and feelings