الفاحشة / الفحشاء
al-Fāḥisha, al-Faḥshāʾ
A grave and shameful sin, such as adultery.
What it means
Al-fāḥisha and al-faḥshāʾ name an act so gross that it offends both revelation and decency. The Quran uses the word for adultery: “Do not approach adultery; it is an indecency and an evil way” (17:32). It also says that God has forbidden “shameful deeds, whether open or hidden” (7:33), which shows that the term covers private wrongs as well as public ones.
Scholars read it as a class of major sins with a fixed penalty or a strong moral censure, and adultery is the clearest case. The Quran links prayer with the restraint of such conduct: “Prayer keeps one away from indecency and what is wrong” (29:45). The plural fawāḥish is used for these deeds in general. The word therefore serves as a standing warning against the gravest moral failings.
Often misunderstood as
Translated as “immorality” or “lewdness”, which can suggest a matter of taste; the Arabic names an act of grave sin that God has forbidden.
Term and Arabic as listed in Ismail al Faruqi, Toward Islamic English (International Institute of Islamic Thought, 1995), p. 43, listed as AL FĀḤISHAH, AL FAḤSHĀ'. The definition is restated here.