Erection of the hairs on the surface of the skin, used by furry animals to conserve heat and by some animals (e.g., cats) as a threat display. In humans, piloerection is manifest as "goosebumps," although, since humans lack full body hair, the response is largely vestigial.

when cat's hair stands on end in response to a threatening situation.

Standing up of the body hair.

"goose bumps"