This is the 17704th most frequent Polish word.
zmęczycie
"Zmęczycie" means "you will tire" (second person plural, future tense).
The word 'zmęczycie' is used to indicate the future action of getting tired by the subject, in the second person plural.
Jeśli nie odpoczniecie, zmęczycie się jeszcze bardziej.
If you don't rest, you will tire yourself even more.
Here, 'zmęczycie' predicts the outcome of an action (the walk), relevant to the second person plural subjects.
Kiedy skończycie ten długi spacer, na pewno się zmęczycie.
When you finish this long walk, you will definitely get tired.
In this sentence, 'zmęczycie' expresses a causative future action by others regarding the first person singular.