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.
Bareback, or no condom
professional
water sports
OHAC mean in Relationship
friends with benefits.
In Search Of
"short Message service" in other words text. It's not exclusive to personal ads.
PNP in personal ads means party and play.