A spare bedroom is a room in a house or an apartment that has an extra bed, which can be used by guests when they visit. It usually means there's an additional sleeping area beyond what is needed for the residents of the home.
When we moved here 7 years ago, I claimed this little spare bedroom as my home office. (hookedonhouses.net)
For example, a warm spare bedroom or laundry room is an excellent place to foster a cat or kittens. (sspca.org)
You don't need to have a whole room dedicated to your work — even a nook carved out of the family room or spare bedroom count toward that home - office write off. (rismedia.com)