sexual union(n = noun.act) conjugation, coupling, mating, pairing, union - the act of pairing a male and female for reproductive purposes; "the casual couplings of adolescents"; "the mating of some species occurs only in the spring"
is a kind of sex, sex activity, sexual activity, sexual practice
has particulars: assortative mating, disassortative mating, cross, crossbreeding, crossing, hybridisation, hybridization, hybridizing, interbreeding, inbreeding, service, servicing

N  sex, sexuality, gender, male, masculinity, maleness, female, femininity, sexual intercourse, copulation, mating, coitus, sex, lovemaking, marital relations, sexual union, sleeping together, carnal knowledge, sex instinct, sex drive, libido, lust, concupiscence, hots, horns, arousal, heat, rut, estrus, oestrus, tumescence, erection, hard-on, boner, masturbation, self-gratification, autoeroticism, onanism, self- abuse, orgasm, climax, ejaculation, sexiness, attractiveness, sensuality, voluptuousness, fornication, adultery, sex symbol, sex goddess, stud, hunk, one-night stand, pornography, porn, porno, hardcore pornography, softcore pornography, pin-up, cheesecake, beefcake, Playboy, Esquire, Hustler, perversion, deviation, sexual abnormality, fetish, fetishism, homosexuality, lesbianism, bisexuality, sodomy, buggery, pederasty, sadism, masochism, sado-masochism, incest, sexy, erotic, sexual, carnal, sensual, hot, horny, randy, rutting, passionate, lusty, hot-blooded, libidinous, up, in the mood, homosexual, gay, lesbian, bisexual.

art union, civil union, company union, constitutional union party, cooper union, cooper union for the advancement of science and ar, craft union, credit union, customs union, double standard of sexual behavior, european union, industrial union, labor union, pan american union, primary sexual characteristic, secondary sexual characteristic, sexual, sexual abstention, sexual abuse, sexual activity, sexual arousal, sexual assault, sexual characteristic, sexual climax, sexual congress, sexual conquest, sexual desire, sexual discrimination, sexual harassment, sexual immorality, sexual intercourse, sexual inversion, sexual love, sexual morality, sexual perversion, sexual pleasure, sexual practice, sexual preference, sexual relation, sexual relationship, sexual reproduction, sexual urge, soviet union, student union, teamsters union, trade union, trade union movement, trades union, union, union army, union card, union flag, union jack, union member, union of burma, union of serbia and montenegro, union of soviet socialist republics, union representative, union shop, union soldier, union suit, vertical union, woman's christian temperance union