is the most straightforward translation of "dirty". It's used both literally (e.g., , , ) and figuratively (e.g., , , ). It rarely has a sexual connotation. usually refers to a book covered with mud, for example.
When modifies a tangible object, it means "lewd". / usually refers to porn books/movies. But it's more commonly used to describe someone's indecent, disgusting, sarcastic or filthy behavior. may or may not have sexual connotations depending on the context.