Part of Speech: adjective

Definition: relating to tension. capable of being drawn out or stretched.

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 Tensile describes something to be durable because from the definition we can see that the fence was capable of being stretched and it was capable of being drawn out.