a piece of clothing that you obtain as a result of spending the night at someone's place, or them spending the night at your place.
"Damn...where did you get that serape?
"It's a shack prize from that guy who I met last Saturday at the Cinco de Mayo party. He forgot it when he snuck out on Sunday morning."
thick dark facial hairs (on a woman)
I just got some new tweezers, so I spent the morning in front of my magnifying mirror, hunting for wolves.