IPA: /ˌʌnəˈseɪld/
KK: /ʌnəˈseɪld/
Not attacked or challenged in any way; secure or safe from criticism or opposition.
The unassailed champion defended his title with confidence.
Unassailed → It is formed from "un-" (meaning not) and "assail" (from Old French *assailir*, meaning to attack). The word "unassailed" means not attacked or not subjected to assault.
Think of 'not' ('un-') being combined with 'attacked' ('assail') — that's why unassailed means not attacked.