"Runnier" is a comparative form of the adjective "runny," which means a substance that is watery and fluid. Some synonyms for "runnier" are "more liquid," "thinner," "more watery," "more fluid," "more pourable," and "more drippy." Depending on the context, other synonymous terms may include "more diluted," "more viscous," "more liquefied," "more unfettered," or "more meandering." These synonyms are useful in different situations, such as when describing beverages or sauces that are too watery or thin. In short, the word "runnier" can be replaced with many synonymic expressions, depending on the intended meaning and the context of use.