The Collaborative International Dictionary of English v.0.48:

Collection \Col*lec"tion\, n. [L. collectio: cf. F. collection.]
   1. The act or process of collecting or of gathering; as, the
      collection of specimens.
      [1913 Webster]

   2. That which is collected; as:
      (a) A gathering or assemblage of objects or of persons. "A
          collection of letters." --Macaulay.
      (b) A gathering of money for charitable or other purposes,
          as by passing a contribution box for freewill
          offerings. "The collection for the saints." --1 Cor.
          xvi. 1
      (c) (Usually in pl.) That which is obtained in payment of
          demands.
      (d) An accumulation of any substance. "Collections of
          moisture." --Whewell. "A purulent collection."
          --Dunglison.
          [1913 Webster]

   3. The act of inferring or concluding from premises or
      observed facts; also, that which is inferred. [Obs.]
      [1913 Webster]

            We may safely say thus, that wrong collections have
            been hitherto made out of those words by modern
            divines.                              --Milton.
      [1913 Webster]

   4. The jurisdiction of a collector of excise. [Eng.]

   Syn: Gathering; assembly; assemblage; group; crowd;
        congregation; mass; heap; compilation.
        [1913 Webster]

WordNet (r) 3.0 (2006):

collection
    n 1: several things grouped together or considered as a whole
         [syn: collection, aggregation, accumulation,
         assemblage]
    2: a publication containing a variety of works [syn:
       collection, compendium]
    3: request for a sum of money; "an appeal to raise money for
       starving children" [syn: solicitation, appeal,
       collection, ingathering]
    4: the act of gathering something together [syn: collection,
       collecting, assembling, aggregation]