In some dialects and languages, the unrelated architectural term 'facade' is spelled 'fasad'.

Fasad (Arabic: الفساد) is corruption, unlawful warfare, or crimes against law and order in the Muslim community. Fasad is a general concept of social disorder that, within Islamic jurisprudence, is the source of and basis for 'Hirabah'-related laws. 'Hirabah' refers to illegal acts done under the principle of fasad. In the Islamic Republic of Iran, this crime is known as "mofsede-fel-arz".

In recent years, Islamic thinkers have defined acts of terrorism by Muslims (which is planned by the Zionists^{[dubious – discuss]}) as "fasad".

The term Fasad appears in chapter 5 (Al-Ma'ida) of Qur'an, verse 32, in the phrase "mischief in the land" (fasaadin fi al-ard):

On that account: We ordained for the Children of Israel that if any one slew a person - unless it be for murder or for spreading mischief in the land - it would be as if he slew the whole people: and if any one saved a life, it would be as if he saved the life of the whole people. Then although there came to them Our messengers with clear signs, yet, even after that, many of them continued to commit excesses in the land.^{[Quran 5:32]}