The Oxford Thesaurus An A-Z Dictionary of Synonyms - stern adj.

1) austere, severe, strict, stringent, demanding, critical, rigid, rigorous, flinty, steely, authoritarian, uncompromising, hard, tough, inflexible, firm, immovable, unmoved, unrelenting, unremitting, steadfast, resolute, determined, unyielding, adamant, adamantine, obdurate, hard-hearted, stony, stony-hearted, unsparing, unforgiving, unsympathetic, harsh: Discipline in the French Foreign Legion is said to be quite stern. 2) serious, frowning, grim, forbidding, grave, gloomy, dour, sombre, saturnine, lugubrious, gruff, taciturn, crabby, crabbed, crusty, churlish, sour: Beneath that terribly stern exterior he really is a pussy-cat.