'Unnatural' in the Bible

Do you not know that unrighteous men will not inherit God's Kingdom? Cherish no delusion here. Neither fornicators, nor idolaters, nor adulterers, nor any who are guilty of unnatural crime,

So also Sodom and Gomorrah--and the neighboring towns in the same manner--having been guilty of gross fornication and having gone astray in pursuit of unnatural vice, are now before us as a specimen of the fire of the Ages in the punishment which they are undergoing.