1. [n]  a change or alteration in form or qualities
2. [n]  (genetics) any event that changes genetic structure; any alteration in the inherited nucleic acid sequence of the genotype of an organism
3. [n]  (biology) an organism that has characteristics resulting from chromosomal alteration

Mutation
Scientific experiments go awry when a mad doctor starts mixing genes in his laboratory in the hope of cooking up the ideal son. But before the proud new father realizes he`s in over his head, he winds up with a mutated horror on his hands.

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1. \Mu*ta"tion\, n. [L. mutatio, fr. mutare to change: cf.
   F. mutation. See {Mutable}.]
   Change; alteration, either in form or qualities.
         The vicissitude or mutations in the superior globe are
         no fit matter for this present argument. --Bacon.
   

2. \Mu*ta"tion\, n.
   1. (Biol.) Gradual definitely tending variation, such as may
      be observed in a group of organisms in the fossils of
      successive geological levels.
   2. (Biol.)
      (a) As now employed (first by de Vries), a sudden
          variation (the offspring differing from its parents in
          some well-marked character or characters) as
          distinguished from a gradual variations in which the
          new characters become fully developed only in the
          course of many generations. The occurrence of
          mutations, and the hereditary transmission, under some
          conditions, of the characters so appearing, are
          well-established facts; whether the process has played
          an important part in the evolution of the existing
          species and other groups of organisms is a disputed
          question.
      (b) The result of the above process; a suddenly produced
          variation.
   

1. An alteration in DNA structure or sequence of a gene. (See Point mutation)
2. Any heritable change in DNA sequence.
3. an alteration of the genetic material.