The antonyms for the phrase "up neck in" could vary depending on the context this phrase is used. However, some possible antonyms for "up" could be "down," "lower," or "decrease." On the other hand, for "neck in," potential antonyms could be "open up," "expand," or "widen." These antonyms imply the opposite meaning of what "up neck in" portrays, which could suggest tightening or compressing something. By using these antonyms, one can convey the intended message of opposite action, which helps in conveying a clear and precise meaning. Ultimately, knowing both the synonyms and antonyms of various phrases is significant for effective communication.