Porn Without Plot (or Plot? What Plot?) Fanfic of the -errrm- titillating variety. Sometimes slash, sometimes not. Like the name says, Plot is *very* optional. Sex (or sexual activity) is not.
"Plot, What Plot?" or "Porn Without Plot" depending on who you ask. This refers to a fic that is pure smut, without any worthwhile plot or insight.
"Plot-What-Plot?" A story that contains only sex with no messy plot stuff in the way.