A type of jahalah that denotes “excessive or major ignorance/ lack of knowledge” about the object of sale or price (thaman), among others. Jahalah fahishah is classified by jurists into four general categories: (1) ignorance concerning the object of sale, (2) ignorance concerning the price, (3) ignorance regarding the contract duration, and (4) ignorance regarding the means of contract formulation (i.e., recording). Major ignorance is prohibited by shari’a and renders contracts void or defective. Jahalah fahishah may lead to dispute (munaza’ah) between the parties to a contract, and hence the shari’a stance of prohibition.

Examples of sales that are associated with jahalah fahishah are buyu’ al-gharar (gharar sales) such as ba’i al-mulamasah, ba’i al-hasat, ba’i al-munabazhah, ba’i al-malaqeeh, etc.