The phrase "termination shock" refers to the point where something suddenly stops or ends. It can be used to describe the boundary where the influence of a celestial object, like the Sun, decreases rapidly. Full definition
Again, the authors argue that backup systems scattered across multiple nations would reduce the likelihood of termination shock, although the risk can't be eliminated entirely. (earther.com)
There are several ways in which termination shock could be avoided, the researchers argue in their paper. (carbonbrief.org)
Parker, A. and Irvine, P. J. (2018) The risk of termination shock from solar geoengineering, Earth's Future, doi: 10.1002 / 2017EF000735 (carbonbrief.org)