The observation of an anti‐Stokes satellite in the spectrum of light backscattered from a CO2laser plasma is reported. Its origin is found to be Thomson scattering of the incident light from a counterpropagating mode‐coupled plasma wave. The parent electron and ion waves in the mode‐coupling process were driven by stimulated Raman and Brillouin backscattering. The parent and daughter plasma waves were detected by ruby laser Thomson scattering. A computer simulation modeling the experiment shows further cascading of the Stokes backscattered light to lower frequencies, apparently a result of its rescattering from another, higher phase velocity, counterpropagating coupled mode. Comparisons with theoretical predictions are presented.