unaccented

adjective
  1. 1

    Of a word, having no diacritical mark; accentless.

  2. 2

    Of a vowel or syllable, pronounced with no, or little stress.

  3. 3

    Not pronounced with a distinctive accent.

    โ€œThe Frenchman spoke clear, unaccented English.โ€

Source: https://en.wiktionary.org/wiki/unaccented