Intersyllabic refers to something that occurs between syllables in a word. Some possible synonyms for this word include interstitial, intrasyllabic, and intersticial. Other words that might be used to describe something that occurs between syllables include intermedial, intervening, and intersegmental. When talking about the relationships between syllables, words like sub-syllabic, super-syllabic, and inter-syllable might be used as well. In some cases, these synonyms might be more precise or more appropriate depending on the specific context in which they are used. Ultimately, the best synonym for intersyllabic will depend on the nuances of the situation in question.