The Collaborative International Dictionary of English v.0.48:

Coalesce \Co`a*lesce"\, v. i. [imp. & p. p. Coalesced; p. pr.
   & vb. n. Coalescing.] [L. coalescere, coalitium; co- +
   alescere to grow up, incho. fr. alere to nourish. See
   Aliment, n.]
   1. To grow together; to unite by growth into one body; as,
      the parts separated by a wound coalesce.
      [1913 Webster]

   2. To unite in one body or product; to combine into one body
      or community; as, vapors coalesce.
      [1913 Webster]

            The Jews were incapable of coalescing with other
            nations.                              --Campbell.
      [1913 Webster]

            Certain combinations of ideas that, once coalescing,
            could not be shaken loose.            --De Quincey.

   Syn: See Add.
        [1913 Webster]

WordNet (r) 3.0 (2006):

coalesce
    v 1: mix together different elements; "The colors blend well"
         [syn: blend, flux, mix, conflate, commingle,
         immix, fuse, coalesce, meld, combine, merge]
    2: fuse or cause to grow together