naturalization has 1 distinct synonym spread across 4 of its 4 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.
the quality of being brought into conformity with nature
the proceeding whereby a foreigner is granted citizenship
the introduction of animals or plants to places where they flourish but are not indigenous
changing the pronunciation of a borrowed word to agree with the borrowers' phonology
“the naturalization in English of many Italian words”
Synonyms, antonyms and the broader and narrower relations for naturalization come from Princeton University’s WordNet. Full sources and licences.