Adumbratively, meaning in a shadowy or vague way, can be replaced with similar words that convey a similar meaning. One synonym could be obliquely, which indicates a sort of indirectness or unclearness in communication. Another option could be suggestively, which implies a veiled or implicit message. Vaguely is another good option, as it conveys a sense of haziness or ambiguity about something. Additionally, tentatively could work in certain contexts, as it indicates a hesitant or uncommitted approach to something. Ultimately, there are numerous synonyms for adumbratively, each with their own nuances and connotations that can be used effectively in a wide range of contexts.