Unassimilable refers to something that cannot be fully understood or integrated into a particular system or culture. Some synonyms for unassimilable include unintelligible, incomprehensible, unfathomable, and enigmatic. Other similar words include perplexing, mysterious, obscure, cryptic, and inscrutable. Unassimilable can also be described as something that is foreign or alien, so other words that could serve as synonyms include exotic, unfamiliar, and strange. In addition, words like unmanageable, impossible, and impractical could also be considered synonyms for unassimilable, as they reflect a sense of impossibility or difficulty in integrating something into a particular system.