The Collaborative International Dictionary of English v.0.48:

Manifold \Man"i*fold\, a. [AS. manigfeald. See Many, and
   Fold.]
   1. Various in kind or quality; many in number; numerous;
      multiplied; complicated.
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            O Lord, how manifold are thy works!   --Ps. civ. 24.
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            I know your manifold transgressions.  --Amos v. 12.
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   2. Exhibited at divers times or in various ways; -- used to
      qualify nouns in the singular number. "The manifold wisdom
      of God." --Eph. iii. 10. "The manifold grace of God." --1
      Pet. iv. 10.
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   Manifold writing, a process or method by which several
      copies, as of a letter, are simultaneously made, sheets of
      coloring paper being infolded with thin sheets of plain
      paper upon which the marks made by a stylus or a
      type-writer are transferred; writing several copies of a
      document at once by use of carbon paper or the like.
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The Collaborative International Dictionary of English v.0.48:

Manifold \Man"i*fold\, n.
   1. A copy of a writing made by the manifold process.
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   2. (Mech.) A cylindrical pipe fitting, having a number of
      lateral outlets, for connecting one pipe with several
      others; as, the exhaust manifold of an automobile engine.
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   3. pl. The third stomach of a ruminant animal. [Local, U.S.]
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The Collaborative International Dictionary of English v.0.48:

Manifold \Man"i*fold\, v. t. [imp. & p. p. Manifolded; p. pr.
   & vb. n. Manifolding.]
   To take copies of by the process of manifold writing; as, to
   manifold a letter.
   [1913 Webster]

WordNet (r) 3.0 (2006):

manifold
    adj 1: many and varied; having many features or forms; "manifold
           reasons"; "our manifold failings"; "manifold
           intelligence"; "the multiplex opportunities in high
           technology" [syn: manifold, multiplex]
    n 1: a pipe that has several lateral outlets to or from other
         pipes
    2: a lightweight paper used with carbon paper to make multiple
       copies; "an original and two manifolds" [syn: manifold
       paper, manifold]
    3: a set of points such as those of a closed surface or an
       analogue in three or more dimensions
    v 1: make multiple copies of; "multiply a letter"
    2: combine or increase by multiplication; "He managed to
       multiply his profits" [syn: multiply, manifold]

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "manifold":
   allotropic, assorted, divers, diverse, diversified, diversiform,
   heteromorphic, heteromorphous, increased, many, many-sided,
   metamorphic, metamorphotic, miscellaneous, multifarious, multifold,
   multiform, multiphase, multiple, multiplex, multiplied,
   multitudinous, numerous, polymorphic, polymorphous, polynomial,
   protean, proteiform, sundry, varied, various