Austere
Etymology: [F. austère, L. austerus, fr. Gr. Sear.]
1. Sour and astringent; rough to the state; having acerbity; as, an austere crab apple; austere wine.
2. Severe in modes of judging, or living, or acting; rigid; rigorous; stern; as, an austere man, look, life. From whom the austere Etrurian virtue rose. Dryden.
3. Unadorned; unembellished; severely simple.
Syn. -- Harsh; sour; rough; rigid; stern; severe; rigorous; strict.
Shades of meaning
Fernald has no entry of its own for austere; he lists it under severe.
Where he writes about it:
Austere signifies severely simple or temperate, strict in self-restraint or discipline, and similarly unrelenting toward others. — from severe
We speak of austere morality, rigid rules, rigorous discipline, stern commands, severe punishment, harsh speech or a harsh voice, hard requirements, strict injunctions, and strict obedience. — from severe
The austere character is seldom lovely, but it is always strong and may be grand, commanding, and estimable. — from severe