look up any word, like doxx:
 
1.
Acronym for "submissive seme, dominant uke".

In yaoi, a sexual situation with dominance/submission in which the seme (person penetrating) obeys and the uke (being penetrated) decides what happens.
In chapter 3, we finally get to the sex: delicious SSDU.
by emerald lizard May 15, 2008