adj. 25B6; adjective
his grim expression : STERN, forbidding, uninviting, unsmiling, dour, formidable, harsh, steely, flinty, stony; cross, churlish, crabbed, surly, sour, ill-tempered; fierce, ferocious, threatening, menacing, implacable, ruthless, merciless.
grim humour : BLACK, dark, mirthless, bleak, cynical.
the asylum holds some grim secrets : DREADFUL, dire, ghastly, horrible, horrendous, horrid, terrible, awful, appalling, frightful, shocking, unspeakable, grisly, gruesome, hideous, macabre; depressing, distressing, upsetting, worrying, unpleasant.
a grim little hovel : BLEAK, dreary, dismal, dingy, wretched, miserable, depressing, cheerless, comfortless, joyless, gloomy, uninviting; informal God-awful.
grim determination : RESOLUTE, determined, firm, decided, steadfast, dead set; obstinate, stubborn, obdurate, unyielding, intractable, uncompromising, unshakeable, unrelenting, relentless, dogged, tenacious.
amiable, pleasant.