The form of the word used here (מֹרְאָה) is unusual. Some English versions prefer the translation “filthy” (KJV, NET, NRSV), which assumes that the word used is derived from a word that means “soiled, excrement, sullied” (מָרָא). The word that follows, “defiled,” would support this interpretation. But the ESV, NASB, and NIV follow the traditional route of translating the word as “rebellious,” understanding the word to derive from מָרָה (“to rebel”). This points to covenant rebellion, which is outlined in verse Zephaniah 3:2. This is the preferable translation.