So difficult or taxing as to make one exhausted; backbreaking.(adjective)
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Use "gruelling" in a sentence
"Instead of giving their chapters proper titles, these worthy gentlemen simply slap a character’s name at the top of a fresh page, followed by his or her inmost thoughts and experiences in gruelling detail."
"Like most top chefs, his lifestyle could already be described as gruelling, starting work at 7am and finishing at 11pm after dinner."
"Multiple call-backs are rare and long "gruelling" auditions even rarer."