Word Study
gruelling
CIDE DICTIONARY
gruelling, adj.
characterized by toilsome effort; requiring extreme physical or mental effort; as, a grueling campaign. [WordNet 1.5]
OXFORD DICTIONARY
gruelling, adj. & n. (US grueling)
--adj. extremely demanding, severe, or tiring.
--n. a harsh or exhausting experience; punishment.
--adj. extremely demanding, severe, or tiring.
--n. a harsh or exhausting experience; punishment.
Derivative
gruellingly adv.
Etymology
GRUEL as verb, = exhaust, punish
For further exploring for "gruelling" in Webster Dictionary Online