What is "indecency" (faḥshāʾ) referring to in this āyah?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

As for "al-fahshāʾ" (indecency), derived from the verb faḥusha meaning 'to exceed proper bounds,' there are five interpretations:

1. It refers to every sin that carries a prescribed punishment in this world.
2. It signifies acts that are unacceptable to any religious law or tradition.
3. It means stinginess. [These first three views are attributed to Ibn ʿAbbās]
4. It specifically denotes adultery. [Al-Suddī]
5. It encompasses all forms of sins. [Muqātil]