British spelling variant of 'grueler'; a person or thing that exhausts or severely tests others.
British English spelling of 'grueler', using the doubled 'l' that typically appears in British spellings before suffixes like '-er' (compare 'traveller' vs. American 'traveler').
Interestingly, the British 'grueller' spelling feels more intense—the doubled 'l' makes it look heavier and more formidable, which perfectly matches what a grueller *does*!
Complete word intelligence in one call. Free tier — 50 lookups/day.