man·i·fold / ˈmanəˌfōld/ • adj. many and various: the implications of this decision were manifold. ∎ having many different forms or elements: the appeal of the crusade was manifold.• n. 1. a pipe or chamber branching into several openings: the pipeline manifold. ∎ (in an internal combustion engine) the part conveying air and fuel from the carburetor to the cylinders or that leading from the cylinders to the exhaust pipe: the exhaust manifold.2. technical something with many different parts or forms, in particular: ∎ Math. a collection of points forming a certain kind of set, such as those of a topologically closed surface or an analog of this in three or more dimensions. ∎ (in Kantian philosophy) the sum of the particulars furnished by sense before they have been unified by the synthesis of the understanding.DERIVATIVES: man·i·fold·ly adv.man·i·fold·ness n.