The Collaborative International Dictionary of English v.0.48:

nucleic acid \nu*cle"ic ac"id\ (n[=oo]*kl[=a]"[i^]k [a^]s"[i^]d
   or n[=oo]*kl[=e]"[i^]k), n. (Chem., Biochem., Genetics)
   A natural or synthetic polymer consisting of chains of
   ribonucleotide or deoxyribonucleotide units.

   Note: The nucleic acids are vital constituents of all living
         cells, carrying the genetic information propagated
         between generations, and, while a cell is alive, having
         a continued function in coding for the amino acid
         sequence of proteins being synthesized by the cell. The
         two natural types of nucleic adic are ribonucleic
         acid (RNA) and deoxyribonucleic acid (DNA).
         [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

nucleic acid
    n 1: (biochemistry) any of various macromolecules composed of
         nucleotide chains that are vital constituents of all living
         cells