1. (adj.)grim stern and admitting of no compromise; harsh; unyielding: grim determination.
2. grim of a sinister or ghastly character: a grim joke.
3. grim having a harsh, surly, forbidding, or morbid air: a grim countenance.
4. grim fierce, savage, or cruel: War is a grim business.
Definition of 'grim'
Princeton's WordNet
1. (adj)grim, inexorable, relentless, stern, unappeasable, unforgiving, unrelenting not to be placated or appeased or moved by entreaty "grim determination"; "grim necessity"; "Russia's final hour, it seemed, approached with inexorable certainty"; "relentless persecution"; "the stern demands of parenthood"
2. (adj)ghastly, grim, grisly, gruesome, macabre, sick shockingly repellent; inspiring horror "ghastly wounds"; "the grim aftermath of the bombing"; "the grim task of burying the victims"; "a grisly murder"; "gruesome evidence of human sacrifice"; "macabre tales of war and plague in the Middle ages"; "macabre tortures conceived by madmen"
3. (adj)black, grim, mordant harshly ironic or sinister "black humor"; "a grim joke"; "grim laughter"; "fun ranging from slapstick clowning ... to savage mordant wit"
4. (adj)dour, forbidding, grim harshly uninviting or formidable in manner or appearance "a dour, self-sacrificing life"; "a forbidding scowl"; "a grim man loving duty more than humanity"; "undoubtedly the grimmest part of him was his iron claw"- J.M.Barrie
5. (adj)gloomy, grim, blue, depressed, dispirited, down(p), downcast, downhearted, down in the mouth, low, low-spirited filled with melancholy and despondency "gloomy at the thought of what he had to face"; "gloomy predictions"; "a gloomy silence"; "took a grim view of the economy"; "the darkening mood"; "lonely and blue in a strange city"; "depressed by the loss of his job"; "a dispirited and resigned expression on her face"; "downcast after his defeat"; "feeling discouraged and downhearted"
6. (adj)blue, dark, dingy, disconsolate, dismal, gloomy, grim, sorry, drab, drear, dreary causing dejection "a blue day"; "the dark days of the war"; "a week of rainy depressing weather"; "a disconsolate winter landscape"; "the first dismal dispiriting days of November"; "a dark gloomy day"; "grim rainy weather"
Definitions of grim 
Afrikaans: grimmige, wrede
Arabic: كَريه، مُثير للإشْمِئْزاز
Bulgarian: зловещ
Brazilian: terrível
Czech: příšerný, neradostný
German: schrecklich
Danish: grusom; barsk
Greek: φρικτός, δυσάρεστος
Spanish: horrible, horroroso, maca
Estonian: peletav
Farsi: دلخراش؛ ناخوشایند
Finnish: epämiellyttävä
French: sinistre
Hebrew: נוֹרָאִי
Hindi: भयानक
Croatian: strašan, turoban
Hungarian: félelmetes
Indonesian: mengerikan
Icelandic: andstyggilegur,óhugnanleg
Italian: macabro
Japanese: ぞっとするような
Korean: 무서운
Lithuanian: siaubingas, bjaurus, atgr
Latvian: drūms; briesmīgs
Malay: susah
Dutch: vreselijk; akelig
Norwegian: forferdelig, nifs, uhygge
Polish: ponury
Persian: دلخراش؛ ناخوشایند
Pashto: بیروونکی
Portuguese: macabro
Romanian: sinistru
Russian: неприятный
Slovak: ponurý, strašný
Slovenian: zoprn
Serbian: sumoran
Swedish: ohygglig
Thai: ร้ายกาจ
Turkish: korkunç
Taiwanese: 令人害怕的, 令人極不愉快的
Ukrainian: жорстокий
Urdu: خشمگیں
Vietnamese: khốc liệt
Chinese: 令人害怕的，讨厌的
