sex

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The property or quality by which organisms are classified as female or male on the basis of their reproductive organs and functions.
2. n. Either of the two divisions, designated female and male, of this classification.
3. n. Females or males considered as a group.
4. n. 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.
5. n. The sexual urge or instinct as it manifests itself in behavior.
6. n. Sexual intercourse.
7. n. The genitals.
8. v. To determine the sex of (an organism).
9. v. Slang To arouse sexually. Often used with up.
10. v. Slang To increase the appeal or attractiveness of. Often used with up.

Century Dictionary and Cyclopedia

1. n. The character of being either male or female; the anatomical and physiological distinction between male and female, evidenced by the physical character of their generative organs, and the part taken by each in the function of reproduction; gender, with reference to living organisms. Sex is properly predicable only of male or female, those organisms which are neither male nor female being sexless or neuter. But the two sexes are often combined in the same individual, then said to be hermaphrodite or monœcious. Sex runs nearly throughout the animal kingdom, even down to the protozoans, with, however, many exceptions here and there among hermaphrodites. The distinction of sex is probably the most profound and most nearly universal single attribute of organized beings, and among the higher animals at least it is accompanied or marked by some psychological as well as physical characteristics. The essential attribute of the male sex is the generation of spermatozoa, that, of the female the generation of ova, accomplished in the one case by a testis or a homologous organ, and in the other by an ovary or a homologous organ. The act of procreation or begetting in the male is the uniting of spermatozoa to an ovum; the corresponding function in the female is the fecundation of an ovum by spermatozoa, resulting in conception or impregnation. The organs by which this result is accomplished are extremely varied in physical character; and various organs which characterize either sex, besides those directly concerned in the reproductive act, are known as secondary sexual characters. See gender, generation, reproduction, and quotation from Buck under sexuality, 1.
2. n. Either one of the two kinds of beings, male and female, which are distinguished by sex; males or females, collectively considered and contrasted.
3. n. Especially, the female sex; womankind, by way of emphasis: generally with the definite article.
4. n. In botany, the character or structure of plants which corresponds to sex in animals, there being, except in the lowest orders, a clear differentiation of male and female elements. In flowering plants the male organ is the stamen, the female the pistil; in cryptogams different designations are used according to the class of plants, as antheridium, archegonium, etc. See male, adjective, 2, and n., 2; female, n., 2 , and adjective, 2; and Linnean system, under Linnean.
5. n. the female sex collectively; womankind.
6. To ascertain the sex of (a specimen of natural history); mark or label as male or female.
7. n. An obsolete or dialectal form of six.

Wiktionary

1. n. countable Either of two main divisions (either female or male) into which many organisms can be placed, according to reproductive function or organs.
2. n. uncountable The distinguishing property, quality, or assemblage of properties by which organisms are classified as female or male on the basis of their reproductive organs and functions; the set of properties by which male is distinguished from female.
3. n. uncountable Sexual intercourse; the act of sexual intercourse.
4. n. euphemistic Genitalia; a penis or vagina.
5. n. obsolete Women; womankind.
6. v. zoology To determine the biological sex of an animal.
7. v. colloquial To have sex with.

GNU Webster's 1913

1. n. The distinguishing peculiarity of male or female in both animals and plants; the physical difference between male and female; the assemblage of properties or qualities by which male is distinguished from female.
2. n. One of the two divisions of organic beings formed on the distinction of male and female.
3. n. The capability in plants of fertilizing or of being fertilized.
4. n. One of the groups founded on this distinction.

WordNet 3.0

1. n. either of the two categories (male or female) into which most organisms are divided
2. n. the properties that distinguish organisms on the basis of their reproductive roles
3. n. activities associated with sexual intercourse
4. v. stimulate sexually
5. v. tell the sex (of young chickens)
6. n. all of the feelings resulting from the urge to gratify sexual impulses