Meaning of “sin” - Learner’s Dictionary

sin

noun uk us /sɪn/
RELIGION [ C, U ]

something that is against the rules of a religion:

the sin of pride
MORALLY WRONG [ no plural ] informal

something that you should not do because it is morally wrong:

You've only got one life and it's a sin to waste it.

(Definition of “sin noun” from the Cambridge Learner’s Dictionary © Cambridge University Press)