(thing) by rangek Mon Mar 03 2003 at 5:01:55

A molecule with a different set of isotopes in it. Some isopotologues of C2H5OH are shown below: 

    H H           H H         H D
    | |           | |         | |
  H-C-C-O-D     D-C-C-O-D   D-C-C-O-H
    | |           | |         | |
    H H           H H         D H

Isotopologues should not be confused with isotopomers.

http://www.iupac.org/goldbook/I03351.pdf

I like it!