As seen online:
“Cis-lunar space (Latin for “on this side of the moon”) is the spherical volume that extends outward from Earth’s geosynchronous region to encapsulate the moon’s orbit and its Lagrange points, or “L points”—defined as the locations where the combined gravitational acceleration due to the Earth and moon allow a small object, such as a spacecraft, to orbit the Earth at the same rate as the moon.”
— from Cis-lunar space and the security dilemma - Bulletin of the Atomic Scientists as of 9 February 2026