The antonym for "un-graspable" would be "graspable" or "perceivable." If something is graspable, it means that it can be easily understood or comprehended. On the other hand, a thing that is un-graspable is usually vague or abstract, making it difficult to grasp or comprehend. Another antonym for "un-graspable" could be "tangible," as it describes something that can be physically touched or felt, allowing for greater understanding and comprehension. Similarly, the term "concrete" could also be an antonym for "un-graspable," as it refers to ideas or thoughts that are clear and well-defined.