IPA: /ʌnˈdɪmd/
KK: /ʌnˈdɪmd/
Not reduced in brightness or intensity; remaining clear and strong.
The stars shone undimmed in the night sky despite the city lights.
Undimmed → It is formed from "un-" (meaning not) and "dimmed" (from Old English "dimmian", meaning to make dim or dark). The word "undimmed" means not made dim or not darkened.
Think of 'not' ('un-') making something 'dim' or dark, so 'undimmed' means it remains bright or clear.