IPA: /ˌʌn.dɪˈmɪn.ɪʃt/
KK: /ʌnˈdɪmɪnɪʃt/
Not reduced in amount, strength, or quality; remaining the same as before.
Her enthusiasm for the project remained undiminished even after several setbacks.
Undiminished → It is formed from "un-" (meaning not) and "diminished" (from Latin "diminuere", meaning to lessen). The word "undiminished" means not lessened or reduced in any way.
Think of 'not' ('un-') and 'lessened' ('diminished') to remember that 'undiminished' means something that has not been reduced.