gruelling UK /ˈɡɹʊə.lɪŋ/US /ˈɡɹu.lɪŋ/noun 2adjective 1forms 3 noun2 •A race in which the animal being raced finishes in a state of physical exhaustion.The course was given to the black puppy, but his chance was generally considered to have been utterly destroyed by the two gruellings he had received. — 1907 •A gruelling ordeal.'Give me a buzz when you think you can squeeze me in between English lit and the pinball championships and the gruellings of overwork, OK?' — 2005 adjective1 •Very difficult or taxing; exhausting; backbreaking. formsgruellings · more gruelling · most gruelling