"Pressure oscillations" refers to the regular and repeated changes in pressure levels. It means that the pressure goes up and down rapidly, like a wave or vibration. Full definition
Theory predicts stronger lunar pressure oscillations in the tropics but their amplitude rarely exceeds 100 microbars or 0.01 percent of the average surface pressure. (scientificamerican.com)
The study's computer simulations show a decadal on - off pattern of correlated changes in the polar vortex, atmospheric pressure oscillations over the North Atlantic and changes in sea circulation more than one mile beneath the waves. (environmentalresearchweb.org)
Worse, the process failed to filter out the random pressure oscillations («gravity waves») that show up in the complete solution of equations for a fluid. (history.aip.org)