The Collaborative International Dictionary of English v.0.48:

octanucleotide \oc`ta*nu"cle*o*tide\
   ([o^]k`t[u^]*n[=u]"kl[=e]*[-o]*t[imac]d), n. [Octa- +
   nucleotide.] (Chem.)
   A molecule composed of eight nucleotide units bound to each
   other by phosphodiester bonds in a linear array; as, a
   partial digest of DNA or RNA may include octanucleotides. See
   octamer.
   [PJC]