Part of Speech: noun
Definition: a soft luster on a surface.
Source: Words at Dictionary
Discovering colors in Prison by Nancy Gomez, line 9
“The cold, tensile sheen/ that buzzes off the electrified fence, the color of barbs/ in barbed wire.”
The word “Sheen” describes a lustered surface to feel soft. The author is describing the electric fence and the barb wires in the poem.