In a revised edition of this catechism, there is a different answer given to this question. I’ve given that one in the first comment on this post and I hope you’ll tell me which answer you think is better.
Part III: Questions about Salvation
93. Q. What is righteousness? A. It is God’s goodness as revealed in his law, and as honored in Christ’s perfect obedience to that law.
Have you posted a hymn (or sermon, sermon notes, prayer, etc.) today and I missed it? Let me know by leaving a link in the comments or by contacting me using the contact form linked above, and I’ll add your post to the list.