Insuperability refers to the state of being impossible to overcome. Some synonyms for this word include invincibility, unassailability, indestructibility, impregnability, and immovability. Invincibility suggests a sense of unbeatability, while unassailability stresses the point of being unchallengeable. Indestructibility refers to the quality of being impossible to destroy, while impregnability indicates a state of being unpenetrable. Immovability, on the other hand, suggests a lack of flexibility or inability to change. All these words convey a similar idea of being unconquerable or unyielding, certain aspects that are hard to overcome, whether it's a physical, emotional, or intellectual barrier.