This terminology came up in the 1965 Sci-Fi movie - Mutiny in Space.
Ai explanation - It appears there might be a slight mix-up or a combination of two entirely different concepts in your phrase “trilithic delineator.”
If you are working in telecommunications, Trilithic is a widely known manufacturer of broadband, RF, and cable TV testing equipment.
They are famous for tools which are RF signal leakage detectors used by field technicians to “delineate” or pinpoint where signals are escaping from cable systems.
If you are working in road construction or facility safety, a delineator is a physical traffic guidance marker.
These are highly visible, reflective plastic or steel posts used to guide vehicles, outline lanes, and manage crowds.
