In gay ads, "FF" typically stands for "femme-to-femme," referring to women who are feminine in their presentation and behavior. It is often used to indicate a preference for feminine women in terms of romantic or sexual attraction.
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