1.
If you describe something as obscene, you mean it offends you because it relates to sex or violence in a way that you think is unpleasant and shocking.
I'm not prudish but I think these photographs are obscene...
He continued to use obscene language and also to make threats.
ADJ
2.
In legal contexts, books, pictures, or films which are judged obscene are illegal because they deal with sex or violence in a way that is considered offensive to the general public.
A city magistrate ruled that the novel was obscene and copies should be destroyed...
ADJ
3.
If you describe something as obscene, you disapprove of it very strongly and consider it to be offensive or immoral.
It was obscene to spend millions producing unwanted food...
= offensive
ADJ: oft it v-link ADJ to-inf/that [disapproval]