To make natural
To make (a word) a natural part of the language, using the native homologue of each phoneme (and often for each morpheme) of the imported word (e.g., native inflections).
To study nature.
To limit explanations of a phenomenon to naturalistic ones and exclude supernatural ones.
To grant citizenship to someone not born a citizen.
To acclimatize an animal or plant.
To restore to freshness or vigor.
To renew; to revamp something to make it look new again.