verb To grant citizenship to someone not born a citizen.
verb To acclimatize an animal or plant.
verb To make natural.
Custom naturalizes labour or study.
verb To limit explanations of a phenomenon to naturalistic ones and exclude supernatural ones.
verb 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).
In English, foreign words are typically written in italics until they are naturalized.
verb To study nature.
verb ↑ "naturalize" in Dictionary.com Unabridged. Random House, Inc.