There is no commonly accepted definition of the word "longful," which means there are no synonyms specific to this term. However, within different contexts, some words that might be considered similar to "longful" are "longing," "yearning," "desiring," and "craving." These terms all suggest a strong desire or a sense of lacking something that one desires. Other words that could be associated with "longful" might include "wistful," "nostalgic," or "languishing," all of which connote a sense of longing for something that is out of reach. Ultimately, it's up to the individual to determine the most appropriate synonym for the word "longful" based on the context in which it is being used.