plain lacking embellishment or ornamentation; "a plain hair style"; "unembellished white walls"; "functional architecture featuring stark unornamented concrete"
austere -
of a stern or strict bearing or demeanor; forbidding in aspect; "an austere expression"; "a stern face"
austere -
practicing great self-denial; "Be systematically ascetic...do...something for no other reason than that you would rather not do it"- William James; "a desert nomad's austere life"; "a spartan diet"; "a spartan existence"
abstemious sparing in consumption of especially food and drink; "the pleasures of the table, never of much consequence to one naturally abstemious"- John Galsworthy
