I heard that in the past, around the 1980s, people could be executed for this. But what does it consist of? Is there an english/american equivalent or something similar?
黑灯舞 sounds like the direct translation of 'Black Light Dance' a.k.a. 'U V Light Dance.' (dancing in darkness with U V Light on)
But according to this article 黑灯舞 refers to "dancing in a dancing hall under very dim light"
黑灯舞, in this case, should be translated as "(indecently) dance in the darkness" (darkness make it easier for people to have indecent physical contact)
I think many people nowadays would use 黑灯舞 as the modern term for 'Black Light Dance'