Gruelling means exhausting and long. A gruelling race, gruelling hours, a gruelling schedule.
The length is essential — a hard moment is not gruelling, but a hard week is. It comes from gruel, the thin porridge, through an old slang verb meaning to punish. Note the American spelling grueling with one l.
1adjectivegruellingExhausting and long.
“A gruelling ninety hours over four days.”
gruelling is a quality of hardship.
Also accepted in games: grueling
From an old slang verb to gruel, meaning to punish or exhaust, from gruel, the thin porridge given to the poor.
by surface analysis, gruel + -ing.
Etymology from Wiktionary, CC BY-SA