The phrase "between lines" is often used to describe meaning or messages that are not explicitly stated. There are a few synonyms that can be used to convey this concept, such as "implicit," "unstated," or "implied." These words suggest that there is additional meaning beyond the surface level of written or spoken words. Other possible synonyms for "between lines" include "subtext," "undertone," or "undercurrent." Each of these words points to the idea that there is a deeper layer of meaning that can be inferred or interpreted from what is directly expressed.