Disgustingly desperate, double date. are all things I've read attributed to the meaning of DD. But it actually means Drug and Disease (free) in other words they have no sexually transmitted disease and they don't use drugs. I hope this helps?
It can also mean Domestic Discipline, D's is Dominance and submission.
In the personal ads that I have seen, LOS means Lost or Stolen.
Androgynous
For sex :)
Long Term RelationshipLTR in personal ads means long term relationship.
professional
water sports
Bareback, or no condom
OHAC mean in Relationship
In Search Of
friends with benefits.
Pay to play
"short Message service" in other words text. It's not exclusive to personal ads.