O, Os

Orgasm, orgasms.

Obstetrician-Gynecologist
A Physician with a specific focus on women's health.
Obstetrics
The branch of medicine that involves care of a woman during pregnancy, during labor and delivery, and after childbirth.
Ocular Herpes
A herpes infection in the eye.

Off-the-clock

Activities that occur with a provider that she chooses not to charge for. (e.g. "We had lunch off-the-clock")
OKP

Or-Kui-Poh - It means a Female pimp in Hokkien, a Chinese dialect, but sometimes people use OKP/OKT to describe a supervisory person who will guide you in your selection of girls in a spa.

OKT

Or-Kui-Tao - It means a Male pimp in Hokkien, a Chinese dialect, but sometimes people use OKP/OKT to describe a supervisory person who will guide you in your selection of girls in a spa.
Oligomenorrhea
Infrequent menstrual periods.
Oligospermia / Oligozoospermia
A sperm count below 20 million; a low sperm count; a sperm count low enough to cause a fertility problem.

OMFIAMP

One Man's Food Is Another Man's Posion, (pronounced "Ohm-Fam")
Omnisexual
A person who is attracted to all sexes.

ONS

One NightStand
One Night Stand
Slang for a one time sexual encounter.
On The Rag
Slang for menstruation.
Onanism
Outdated term for masturbation.
Open Facial Herpes
The presence of latent herpes simplex infection in the trigeminal ganglion, at the top of the spine.
Open Relationship
The term for a relationship in which both partners have agreed to date or have sex with other people.

Oral
Short for oral sex
Oral Contraceptive
Another term for a birth control pill.
Oral Sex
The act of stimulating the genitals with the tongue, lips or mouth.
Orgasm
A discharge of neuromuscular tension at the peak of sexual arousal that is usually accompanied by the ejaculation of semen in the male and by vaginal contractions in the female.

OTK

Over The Knee. The position in which one gives or receives a spanking.

OTOH

On the Other Hand

Outcall

Escort sessions where the appointment is scheduled at the customers's home, apartment or hotel room.
Outercourse
Sexual Activity that does not include inserting the penis in the vagina or anus.

Out, Outed

Private, personal information on a hobbyist or provider is made public. e.g. Someone's real name and address is posted to a public forum.
Ovarian Reserve
The number and quality of eggs remaining in a woman.
Over-the-Counter
A medication that is available without a prescription.

OVN

Overnight
Ovulatory Failure
The failure to ovulate.
Ovulation Induction
The use of medication to artificially release several eggs at once to increase the likelihood of conception.
Ovum
The reproductive cell from the ovary that contains the woman's genetic information.
OWO
Slang for "Oral Without Condom".
OWOTC

Oral Without Condom To Completion