Other forms: nominalized; nominalizing; nominalizes
To nominalize is to take a verb, adjective, or other part of speech and transform it into a noun. One of the most common ways to nominalize is by adding -ing to a verb, changing "walk" to "walking."
Nominalize is from nominal, "pertaining to nouns," and its Latin root, nomen, "name." Some words are nominalized by adding a suffix — and there are dozens of these endings, including -ing, -tion and -ity. It's good to watch out for places where you nominalize, because this can make your writing dull and passive. "I came to the decision to eat lunch," which nominalizes "decide" into "decision," is less direct than "I decided to eat lunch."