NCO,
I hope this answers your question.
Aside from how people may have “once thought about” sin, I think the best definition of it appears in the new Catechism of the Catholic Church Nos. 1849-1850:
“Sin is an offense against reason, truth, and right conscience; it is failure in genuine love for God and neighbor caused by a pervasive attachment to certain goods. It woulds the nature of man an injures the human solidarity. It has been defined as 'an utterance, a deed, or a desire contrary to the eternal law.”
“Sin is an offense against God . . . Sin sets itself against God’s love for us and turns our hearts away from it. Like the first sin, it is disobedience, a revolt against God through the will to become ‘like gods’, knowing and determining good and evil. Sin is thus ‘love of onself even to contempt of God.’ In this proud self-exaltation, sin is diametically opposed to the obedience of Jesus, which achieves our salvation.”
I think the above definition/characterization of “sin” will be valid in any time of history, no matter what the period or circumstances.
If I missed what you were looking for, I apologize.