1. 1. The property or quality by which organisms are classified as female or male on the basis of their reproductive organs and functions.
   2. Either of the two divisions, designated female and male, of this classification.
2. Females or males considered as a group.
3. The condition or character of being female or male; the physiological, functional, and psychological differences that distinguish the female and the male. See Usage Note at gender.
4. The sexual urge or instinct as it manifests itself in behavior.
5. Sexual intercourse.
6. The genitals.

1. To determine the sex of (an organism).
2. Slang.
   1. To arouse sexually. Often used with up.
   2. To increase the appeal or attractiveness of. Often used with up.

[Middle English, from Latin sexus.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.