The Collaborative International Dictionary of English v.0.48:

deoxyribonucleic acid \deoxyribonucleic acid\ n.
   a nucleic acid, usually of very high molecular weight,
   consisting of a linear sequence of monomer units of
   deoxyribonucleotides, occurring in most organisms in pairs of
   strands, wound together in the form of a double helix; it is
   the main component of chromosomes and contains the genetic
   information which is the basis of heredity, transmitted from
   parent to progeny, and found in all living organisms except
   for certain viruses which have RNA as their basic genetic
   material; -- usually referred to by the acronym DNA.

   Syn: DNA, desoxyribonucleic acid.
        [PJC]

   Note: The monomer units making up the DNA each contain one of
         four heterocyclic bases: thymine, adenine, cytosine, or
         guanine. The genetic information is contained in the
         precise sequence of these monomer units, which
         ultimately specify the sequence of proteins to be made
         by the organism's biosynthetic processes, mediated
         through the synthesis of RNA having a base sequence
         corresponding to that of the DNA. The DNA sequence also
         specifies the sequence of the various RNA molecules the
         RNA base sequence being a copy of that on one of the
         DNA strands. Most of the RNA synthesized is involved in
         protein synthesis. In the double-helical form of DNA,
         the thymine on one strand is paired with the adenine on
         the opposite strand, and cytosine of one strand is
         paired with guanine on the opposite strand. There is in
         DNA also certain controlling information concerning the
         timing and amount of RNA to be made, encoded within the
         sequence of the DNA in ways that are still being
         elucidated.
         When this structure is replicated in the course of cell
         multiplication, two identical double-helical molecules
         are formed, each containing one strand from the
         original molecule. Each resulting molecule is
         distributred to either the parent or progeny organism,
         and this is the basic mechanism for transmission of
         hereditary information. In RNA-based viruses, or those
         having single strands of DNA (as certain viruses), the
         genetic information transmission occurs through a
         double-stranded intermediate by a similar mechanism.
         In some organisms slight modifications of the bases of
         DNA are found, such as methylcytosine or, in some
         viruses, uracil or hydroxymethyluracil; these unusual
         bases act analogously to the normal bases in their
         genetic coding function. A small percentage of
         methylcytosine is found in many organisms, and it
         serves in some cases as a special signal, as for
         restriction enzymes.
         [PJC]

WordNet (r) 3.0 (2006):

deoxyribonucleic acid
    n 1: (biochemistry) a long linear polymer found in the nucleus
         of a cell and formed from nucleotides and shaped like a
         double helix; associated with the transmission of genetic
         information; "DNA is the king of molecules" [syn:
         deoxyribonucleic acid, desoxyribonucleic acid, DNA]