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This may be a slightly inaccurate answer. From this PlayerStage page it's clear that retro Laser refers to the reflectiveness of the surface in question. From Wikipedia it's clear that a RetroReflector reflects light back with minimum scattering, much like reflectors on roads.

Summing up, I feel that laser retro measures the extent to which the material reflects laser light with minimal scattering. The notion of laser retro reflectiveness also makes sense , e.g. see here.