فَيْفٌ A place that is even, level, or flat: (Ṣ, O, Ḳ:) or, (Ḳ,) accord. to Lth, (T, O,) a waterless desert, (T, M, O, Ḳ,) such as is even, level, or flat, and wide, or spacious; (T, O;) andفَيْفَاةٌ↓ andفَيفَآءُ↓ (M, Ḳ) andفَيْفَى↓ (Ḳ) also signify [thus, or] a waterless desert: (M. Ḳ:) and, (Ḳ,) accord. to El-Mu-arrij, (T, O,) فَيْفٌ signifies a portion of the earth that is a place whereof the winds are variable; (T, O, Ḳ;) and this is the explanation that is preferred by Sh: (T:) and accord. to AA, it signifies [also] any road between two mountains: (T, TA:) its pl. is أَفْيَافٌ [a pl. of pauc.] and فُيُوفٌ [a pl. of mult.]. (T, Ṣ, M, O, Ḳ.)

فَيْفَآءُ is syn. with فَيْفٌ, q. v.: therefore its ا is augmentative, (Ṣ, M,) accord. to Sb (M) and Mbr: (Ṣ:) and it signifies (Ṣ, M, O,) also (M) a smooth [desert such as is termed] صَحْرَآء: (Ṣ, M, O:) its pl. is فَيَافٍ. (Ṣ, M, O, Ḳ. [In the CK, this pl. is written فِيافٌ, as though it were a pl. of فَيْفٌ.])