How to say "obscene": translate 下流 or 輕佻? I want to describe people wearing clothing as totally indecent and obscene, for instance because the clothing doesn’t remotely cover the buttocks. I am not talking about ordinary mini skirts or hot pants.
I definitely want to sound judging and don’t care to be nice to the person in question, but I don’t want the word in itself to be vulgar / unsuitable for use in writing.
I checked dictionaries for 'obscene' and found 下流. My Chinese friend says 下流 is very, very bad and out of proportion and recommended 輕佻, but dictionaries say this means 'skittish, flippant, giddy, frivolous'. These words seem much too cute to me, almost like I am not scolding the person.
How to grasp the difference between the two words?
'Obscene' is not 下流(no class/ bad taste) or 輕佻 (frivolous)

One definition of obscene is 不堪入目 , it is used to describe perverted, immoral act or behavior 

For example: Taking a child from his mother and claim it is all for enforcing the law (which is not true) is an obscene (不堪入耳- too perverted and immoral to the ears) argument

Another definition of obscene is 淫褻 or 不雅 (also means 'unsightly'), it is used to describe extreme sexually suggestive content or display 

I would describe the skirt 不雅, 不堪入目 or 淫褻 if I was judgmental, but I rather call it 大膽 (bold) or 開放 (open)

暴露 (revealing) is also a fitting description of that skirt 

Edit: from all the answers: "下流, 輕佻, 不堪入目, 大膽, 開放, 淫褻, 變態, 不三不四, 有伤风化" are all 'subjective opinions' (you can't say any of them is wrong, but you can disagree with all of them)

Only 暴露 is  an 'objective description' (it is a correct statement based on fact. You can't argue with fact, that skirt does expose a lot of skin)