underscore

/AH0 N D ER0 S K AO1 R/
noun
  1. 1

    An underline; a line drawn or printed beneath text; the character _.

  2. 2

    A piece of background music.

verb
  1. 1

    To underline; to mark a line beneath text.

  2. 2

    To emphasize or draw attention to.

    โ€œI wish to underscore the importance of proper formatting.โ€

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