I've met Christians that will insist they are still sinners.
Here's a fun bit of Bible trivia. Did you know that Sin is the name of a city in Egypt? You'll find it mentioned in Ezekiel 30:15-16.
As pertains to your OP sin is defined by different terms throughout scripture. All pretty much signify the same thing. Missing the mark, an offense, straying from the path of righteousness.
When we were unrepentant sinners that was simply life. Unaware of the righteous path of God we lived our lives with the instruction and examples our family instilled.
When we came to Christ and repented of our sins those were put under his precious blood for all eternity and God holds them against us no more, ever.
Now, as mentioned, we have an advocate for us when we do offend God's right-ness path he's set for us. We're no longer sinners however, we're the saints within the universal church of God. That which divided us is put asunder. There is no Jew, no Greek, no American, no German, etc... we are all one in Christ. 1 Peter 3:11