When it comes to describing something in terms of thousandths, "more millesimal" may not always be the most practical phrase to use. Fortunately, there are plenty of synonyms that can offer precise and effective alternatives. For instance, the term "thousandth" is a common substitution for "millesimal," as is the phrase "per mill." Other options include "parts per thousand," "‰" (the symbol used to denote per mil), and "one-thousandth." Some related phrases could include "thousandth fraction," "fraction of a thousand," or "pertaining to one in a thousand." Ultimately, which synonym is the most suitable will depend on the context and the intended meaning of the term.