Definition of "unassailably"

Blank sightless eyes closed speechless mouth destined eternally to rigid frigidity (frigor mortis). Impenetrable, not an orifice in sight. Inviolably inviolate body unassailably confined within a wall of stone ("leda, lada, aflutter afraida, so does your girdle grow!").

1991, Ailbhe Smyth, “The Floozie in the Jacuzzi”, in Feminist Studies‎, volume 17, number 1

Contrary to his assertion, however, virtually all relevant researchers say the link between CFCs and ozone depletion is based on unassailably solid scientific evidence.

1995, Ross Gelbspan, “The Heat Is On: The Warming of the World’s Climate Sparks a Blaze of Denial”, in Harper's Magazine, footnote 2

[H]owever hard she pushed the tough-talkin' shtick, she remained doe-eyed, glowing and somehow unassailably demure.

2014 January 21, Hermione Hoby, “Julia Roberts interview for August: Osage County – 'I might actually go to hell for this ...': Julia Roberts reveals why her violent, Oscar-nominated performance in August: Osage County made her feel 'like a terrible person' ”, in The Daily Telegraph (Review)‎