Sin is more subtle than missing the mark or disobeying God, the Word, etc., etc. We need not a better definition, but another attribute to carry with our definitions.
Consider: "Thy will be done, on earth as it is in heaven."
That idea, imagination or word - as some would say - carries a tremendous weight of possibilities. But I want to focus on one aspect, that being the idea of a reality. Heaven is a reality distinct from our own, a place where sin does not exist. But just because a reality doesn't look precisely like Heaven, doesn't mean it's sinful.
Consider that all things were created to live, reproduce and die. In other words, things would be born, grow, reproduce, suffer corruption and die - trees, fish, cows, etc., etc. That was the plan, that all would bear fruit after their own kind (Gen. 1:11, ff). Think of it this way: there was always a hungry, bigger fish; or a whale chomping on plankton or sea weed. These are realities distinct from heaven, but not sinful in their own right.
When Adam and Eve sinned, what did they do? They asserted their imagination, their reality contrary to that which was designed. In doing so, they brought upon themselves spiritual separation from God - they created an inferior reality for themselves.
So what's the point? Add to your definition of sin, this: a state of reality expressed that is inferior to purposed design. And in doing so, remember that which is not of faith, is sin - or, inferior to God's design.
So, is cursing sin? Consider it in the context of 1 Corinthians 14:3, "But one who prophesies speaks to men for edification and exhortation and consolation." We can then understand that corrupt communication (Eph. 4:29) is not prophecy.
It is inferior to God's purposed design.