austerest

/AO0 S T EH1 R AH0 S T/
adjective
  1. 1

    Grim or severe in manner or appearance

    โ€œThe headmistress was an austere old woman.โ€

  2. 2

    Lacking decoration; trivial; not extravagant or gaudy

    โ€œThe interior of the church was as austere as the parishioners were dour.โ€

Source: https://en.wiktionary.org/wiki/austere, https://en.wiktionary.org/wiki/austerest