Source : Webster's Revised Unabridged Dictionary (1913)

Formation \For*ma"tion\, n. [L. formatio: cf. F. formation.]
   1. The act of giving form or shape to anything; a forming; a
      shaping. --Beattie.

   2. The manner in which a thing is formed; structure;
      construction; conformation; form; as, the peculiar
      formation of the heart.

   3. A substance formed or deposited.

   4. (Geol.)
      (a) Mineral deposits and rock masses designated with
          reference to their origin; as, the siliceous formation
          about geysers; alluvial formations; marine formations.
      (b) A group of beds of the same age or period; as, the
          Eocene formation.

   5. (Mil.) The arrangement of a body of troops, as in a
      square, column, etc. --Farrow.

Source : WordNet®

formation
     n 1: an arrangement of people or things acting as a unit; "a
          defensive formation"; "a formation of planes"
     2: a particular spatial arrangement
     3: the fabrication of something in a particular shape [syn: {shaping}]
     4: the act of forming something; "the constitution of a PTA
        group last year"; "it was the establishment of his
        reputation"; "he still remembers the organization of the
        club" [syn: {constitution}, {establishment}, {organization},
         {organisation}]
     5: (geology) the geological features of the earth [syn: {geological
        formation}]
     6: natural process that causes something to form; "the
        formation of gas in the intestine"; "the formation of
        crystals"; "the formation of pseudopods"
     7: creation by mental activity; "the formation of sentences";
        "the formation of memories"