Circularizes is a word that typically means to distribute or disseminate information widely, often by sending out circulars or notices. Therefore, one of its antonyms could be "withhold," meaning to keep information or knowledge secret or to refrain from distribution. Another antonym for circularizes could be "restrict," which means to limit or confine something to a specific group or location. Alternatively, an opposite of circularizes could be "conceals" or "hides," which suggests actively preventing information from being shared or publicized. These antonyms help to provide a range of possible meanings of the original word by highlighting the various ways in which information can be disseminated or withheld.