The phrase "most abreast" signifies being up-to-date or informed about the most recent findings or events. Antonyms for this phrase would be words that indicate being uninformed, outdated, or disconnected from current developments. Synonyms such as behind, outmoded, antiquated, ancient, or archaic come to mind. These words suggest a lack of updated knowledge, not staying current or updated, and being out of touch with the latest developments. Using antonyms of "most abreast" can help writers convey a sense of being out-of-date, backward, or old-fashioned, depending on the context.