Homosexual, lesbian (gay) behavior (same sex relationships, marriage…) is sin, and is forbidden in the Bible. The graphic word arsenokoites (from arsen, “male,” and koite, bed) describes a man who “beds” another man. Although arsenokoites is sometimes used in a wide sense referring to all homosexuality, it also had a narrower sense, referring to the one who took the active or “male” role in the homosexual relation. The one who took the passive or “female” role was called the malachos. The word malachos literally means “soft” or “soft to the touch.” Although it had other uses such as “soft clothing,” it was the standard word in the Greek language for the “passive” one in the homosexual relation.
With these terms in mind, as well as others we have encountered above, we see that the vocabulary in 1 Corinthians 6:9 and 10 is very specific: “Neither the sexually immoral (pornos) nor idolaters nor adulterers (moichos) nor male prostitutes (malachos) nor homosexual offenders (arsenokoites) nor thieves nor the greedy nor drunkards nor slanderers nor swindlers will inherit the kingdom of God.” Homosexual behavior is also addressed by descriptive phrases, idioms, and euphemisms rather than just through the words that refer directly to it. For example, Romans 1 contains some very descriptive language.
(24) Therefore God gave them over in the sinful desires of their hearts to sexual impurity for the degrading of their bodies with one another.
(25) They exchanged the truth of God for a lie, and worshiped and served created things rather than the Creator—who is forever praised. Amen.
(26) Because of this, God gave them over to shameful lusts. Even their women exchanged natural relations for unnatural ones.
(27) In the same way, the men also abandoned natural relations with women and were inflamed with lust for one another. Men committed indecent acts with other men, and received in themselves the due penalty for their perversion.
It is hard to read these verses and conclude anything other than that homosexual and lesbian relationships are wrong in God’s sight. The “natural relation” is a man and a woman. Homosexuality is also mentioned idiomatically in Jude 7: “…Sodom and Gomorrah and the cities around them, indulged in gross immorality and went after strange flesh, are exhibited as an example, in undergoing the punishment of eternal fire” (NASB). “Gross immorality” is a good translation of the verb, ekporneuo, which is simply porneuo, the verb meaning, “to commit sexual immorality,” with the prefix ek, which intensifies the verb. Thus, the NASB translation of “gross immorality” is a very good one. Later in the verse, the phrase, “to go after strange flesh” is defined by Louw and Nida in their lexicon as “an idiom, literally ‘to go after strange flesh,’ to engage in unnatural sexual intercourse—‘to have homosexual intercourse.’”  In the Old Testament, the Law forbids homosexuality just as it forbids adultery and bestiality. “Do not lie with a man as one lies with a woman; that is detestable” (Lev. 18:22). “If a man lies with a man as one lies with a woman, both of them have done what is detestable” (Lev. 20:13).
Lesbianism is not specifically mentioned by name in the Bible for a good reason: the name is a late invention. Both the terms “homosexual” and “lesbian” were coined in the 19th century by theorists who were describing people’s emotional and sexual interest for others of the same sex. “Lesbian” was chosen because of Sappho, perhaps the greatest female Greek lyric poet (c. 630-570 BC) who was interested in other women and lived on the island of Lesbos, and from the island of Lesbos itself, because it was known as a center of Greek culture, pleasure and licentiousness. As we saw in the verses just quoted above in Romans, however, the sexual attraction of a woman for another woman instead of a man is not natural and not godly.
1. Johannes Louw and Eugene Nida, Greek-English Lexicon of the New Testament Based on Semantic Domains (United Bible Society, New York, 1989), Vol. 2, p. 772 under aperchomai.