Borescope Question

[prionsa]

Forgive me but i'm not the most familiar with the art of borescoping - what does the term tip substrip mean?

[context - minor tip substrip on hpc blades]

Thanks

[Beeline]

Heard of abraidable buildup on the tip of compressor rotor blades where the tips rub the rotor path lining.

What engine type is it?