12 letters · 14 points in Scrabble
adjective immune to attack; incapable of being tampered with
adjective impossible to assail
adjective without flaws or loopholes
originEtymology tree Proto-Indo-European *né Proto-Indo-European *n̥- Proto-Germanic *un- Proto-West Germanic *un- Old English un- Middle English un- English un- English assailable English unassailable From un- + assailable.
Etymology from Wiktionary, CC BY-SA 3.0