1. A change in the electrical charge between the inside and the outside of a membrane. For example, neurons which are receiving signals become momentarily more positively charged than the outside of their membranes.

  2. The turning of polarized light into random light by reflecting it in all directions, so that it no longer vibrates in a single plane.

From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.