IPA: //ʌnˈtrʌb.əld//
KK: /ʌnˈtrʌbld/
Not disturbed or affected by problems; calm and peaceful.
She felt untroubled by the challenges ahead.
Untroubled → It is formed from "un-" (meaning not) and "troubled" (from Old French *troubler*, meaning to disturb or trouble). The word "untroubled" means not disturbed or free from trouble.
Think of 'not' ('un-') being added to 'disturbed' ('troubled') — that's why untroubled means free from disturbance.