Some words that can define the term "grueling" are: exhausting, tiring, and difficult.
We can arrive at this answer because:
The best way to know how an unknown word can be interpreted is to use synonyms and context clues.
Context clue is the term that refers to the ability of the words in a sentence to promote the context of the sentence, allowing the meaning of an unknown word to be revealed.
Synonyms, in turn, are different words that have similar meanings.
Therefore, to know the context and meaning of a word we must observe the context clue that the text is emitting, as well as test different synonyms, to find the best definition of the word.
Since you haven't shown the sentence this question refers to, it's not possible to determine the exact meaning of the term "grueling," but I hope the above information will help you.
