فسطفُسْطَاطٌ and فِسْطَاطٌ (S, M, Msb, K) and فُسَّاطٌ and فِسَّاطٌ and فُسْتَاطٌ and فِسْتَاطٌ, (S, M, K,) the ت in the last two, as it is not found in the pl., being a substitute for the [former] ط in فسطاط, or rather for the [latter] س in فسّاط, because it is more regular to change the latter of two identical letters than to change the former, and because the two identical letters in فسّاط are together, whereas the two identical letters in فسطاط are separated, (M,) and فُسْتَاتٌ and فِسْتَاتٌ, (K,) altogether eight different forms, but MF observes that Esh-Shiháb El-Kastalánee gives twelve, [which, however, he does not transcribe, the remaining four being probably with fet-h to the ف,] (TA,) A tent of hair [-cloth]: (S, Msb:) or a great tent: (Mgh:) or a kind of structure (M, Z) used in travelling, less than the سُرَادِق: (Z:) or the kind of structure called سُرَادِق: (K:) pl. فَسَاطِيطُ; (M, Msb, TA;) for which they did not say فَسَاتِيطُ. (M, TA:) b2:  Hence فُسْطَاطٌ is applied to A city: (Z, TA:) any city: and particularly a city in which is the general place of assemblage of people: (TA:) a populous, or comprehensive, city; accord. to some: (Msb:) the place of assemblage of the people of a كُورَة [which means a city, and a district, or region], (Lth, Az, K,) around  their general mosque: (Az, TA:) or you say, فُسْطَاطُ المِصْرِ, meaning the place of assemblage of the people of the مصر [or city], around their congregational mosque. (M.) فُسْطَاطُ [so in two copies of the S] is [a name of] The city of مِصْر [the metropolis of Egypt]: (S:) or الفُسْطَاطُ is also the proper name of مِصْرُالعَتِيقَةُ, (K, TA,) the city so called, (TA,) which was built by 'Amr Ibn-El- 'Ás; (K, TA;) the city of مصر in old times; as also الفِسْطَاطُ: (Msb:) and البَصْرَةُ. (TA.)