hair up

verb5

1. •
   (US) To grow (more) hair.
2. •
   (US) To grow its longer, thicker winter coat.

   • Earmarks supplement brands for owner identification. When a cow critter gets all haired up in a thick winter coat, a brand gets harder to read than an earmark. — 1966
3. •
   (US) To grow facial hair, especially after shaving; (rarely) to grow body hair.

   • He ran a hand up the side of his face and winced disapprovingly at the prickle. They wouldn’t let him shave, and he haired up fast. — 1978
4. •
   (US) To cause the fur of (an animal) to puff up or stand on end.

   • “I’m foolish to be roaming around this time of night like an old cat, haired up by the wind. […]” — 1906
5. •
   (US) To soil or mess up (an area, etc.) with hair.

   • “Thank heaven, we’ve had a fire in [the parlor] today,” she thought, “and all I hope is That Cat hasn’t haired up the sofa. If Sarah Pringle got cat hairs on her dress […]” — 1936