Someone with whom you do not have a relationship with but you have mutual sexual relations . Usually using the abbreviation FB, although, FB is sometimes mistaken for Facebook or Finger bang .

Most of the time, both members of the sexual relation are single and their relation is strictly for only that purpose.

It's like Halloween but instead of getting free candy your getting free sex plus there's no feelings involved.

Someone you meet up with occassionally to get frisky. Generally, there are no special feelings attached to them (other than to their genitals). They fulfil your sexual needs...at least a little bit. Haha....

You're not really buddies, you just fuck, usually only as a booty call after you failed to pick up during the 3 o'clock scab grab when last drinks were called at the pub. Dropping the word buddy and replacing it with person (you could use a gender specific noun if desired) is far more appropriate.

Two people who aren't really friends, they are more like acquaintance who just meet up to fuck. They don't hang out or care about each other.

being on and off adn finally just giving up on the boyfriend/girlfriend thing and keepin it physical.

A person you have sex with on a regular basis. However, the relationship is simply only based on sex, nothing more than that.