Obscenity:
Sexually arousing imagery that is considered socially offensive.

Oedipal Conflict:
The Freudian theory that children have an unconscious sexual attachment to the parent of the other gender, causing them to be hostile toward the parent of the same gender.

Oral Contraceptives:
Birth control pills. (OC) A hormone compound that prevents ovulation and thus pregnancy. Usually a progesterone and estrogen compound that is swallowed.

Oral Sex:
Sex play involving the mouth and sex organs.

Orgasm:
Sensory and motor events involved in the ejaculation for the male and involuntary contractions of the perineal muscles in the female at the climax of sexual intercourse.

Outercourse:
Sex play that does not include inserting the penis in the vagina or anus.

Ovary:
The female gonad that produces estrogen, progesterone, and relaxin.

Over-the-counter:
Available without a prescription.

Ovulation:
The rupture of a vesicular ovarian follicle with the release of an egg into the pelvic cavity. – (the time when an ovary releases an egg).

Ovum:
The female reproductive cell; an egg cell.