The Collaborative International Dictionary of English v.0.48:

Intramolecular \In`tra*mo*lec"u*lar\, a.
   1. (Chem. & Physics) Between molecules; situated, or acting,
      between the molecules of bodies. [Obs.]
      [1913 Webster]

   2. Being or occurring within a single molecule; as,
      intramolecular hydrogen bonds.
      [PJC]

WordNet (r) 3.0 (2006):

intramolecular
    adj 1: within the molecule; occurring by a reaction between
           different parts of the same molecule