unassailable

Unassailable is an adjective meaning not able to be attacked, questioned, defeated, or undermined. It is commonly applied to evidence, arguments, or positions that are considered beyond challenge, as well as to physical defenses or fortifications that cannot be readily breached.

The form derives from the prefix un- attached to assailable, which in turn comes from the verb assail, from Old French asailer meaning to attack. The sense of the adjective often emphasizes invulnerability to refutation or attack rather than mere strength.

Usage notes: In formal or analytical writing, unassailable is used with nouns such as evidence, case, or argument. It is similar in meaning to indisputable, incontrovertible, or watertight, but carries a stronger connotation of resilience against attacks or doubts rather than just logical soundness.

Examples: The defense presented an unassailable case for innocence. The scientist cited unassailable data and replicated results to support the theory. The fortress was described as unassailable due to its rugged terrain and robust walls. Her unassailable reputation gave her credibility in the field.

Related terms include indisputable, incontrovertible, watertight, invulnerable, and indefeasible.