脏话
means F-word
or profanity
.
脏
means dirty
, implies sex organs
or sexual intercourse
.
话
means language
or words
.
So the literal meaning of 脏话
is dirty words
.
脏话
stands for some words about sex organs used to insult people, that is to say, profanity
or F-word
.
这里能说脏话吗?
stands for May I speak F-words here?
Also, another example mentioned by user fabregaszy: 我能说脏话吗?不能?那我就没什么可说的。
stands for May I speak F-words? No? Then I have nothing to say.
It shows that the speaker is extremely angry of this decision so I have to say nothing except F-words to the decision maker.