unassailable

un- +‎ assailable

• IPA^(key): /ˌʌnəˈseɪləbl̩/

unassailable (comparative more unassailable, superlative most unassailable)

1. Secure against attack; impregnable.
   • 1599, William Shakespeare, “The Tragedie of Ivlivs Cæsar”, in Mr. William Shakespeares Comedies, Histories, & Tragedies: Published According to the True Originall Copies (First Folio), London: Printed by Isaac Iaggard, and Ed[ward] Blount, published 1623, OCLC 606515358, [Act III, scene i], page 119, column 1:

     Yet in the number, I do know but One / That vnaſſayleable holds on his Ranke, / Vnfhak’d of Motion : and that I am he, / Let me a little ſhew it, euen in this : / That I was conſtant Cymber ſhould be baniſh’d, / And conſtant do remaine to keepe him ſo.

   • 1990, Larry W. Riggs, “Moliere’s “Poststructuralism”: Demolition of Transcendentalist Discourse in Le Tartuffe”, in Symposium: A Quarterly Journal in Modern Literatures, volume 44, number 1, DOI:10.1080/00397709.1990.10733698, page 53:

     His recourse to written documents to make his discourse unassailable has created a virtually unalterable situation even as he is on the verge of being forced to “see through” Tartuffe.

   • 1990, James Brow, “Notes on Community, Hegemony, and the Uses of the Past”, in Anthropological Quarterly, volume 63, number 1, George Washington U Institute for Ethnographic Research, JSTOR 3317955, page 5:

     None of the processes, however, is either uniform or unassailable. The contradictions and distortions within any hegemonic discourse, as well as the discrepancies between it and the popular understandings of common sense, leave it ever vulnerable to penetration, criticism, and refusal.

2. (by extension) Undeniable, incontestable or incontrovertible.

   She won the debate with her unassailable logic.

• (incontestable): unopposable

• unassailably
• unassailableness

unassailable (plural unassailables)

1. Something, such as a belief, that cannot be assailed.