"Slight asymmetry" refers to a small and subtle difference or imbalance between two things that are expected to be similar or symmetric. Full definition
Those particles are particularly fruitful to study because they can be used to probe a very slight asymmetry between matter and antimatter called charge - parity violation, which had only been seen before in particles called K mesons. (sciencemag.org)
Even very slight asymmetries of the neck and torso can make a baby put more weight into one arm or one side of the chest when belly down. (candokiddo.com)
Fixed an issue in Starfirsh Mainstage where placement of obstacles could be slightly off causing slight asymmetry between the two sides of the map. (gonintendo.com)