Definition of “spare” - Learner’s Dictionary

spare

adjective us uk /speər/
Extra Examples
We're going to make the spare room into an office.Are there any spare batteries for my camera?Nigel backed out at the last minute, so we had a spare ticket.It's a good idea to keep a spare key somewhere safe.We need some curtains for the spare bedroom.

B1 If something is spare, it is available to use, because it is extra and not being used:

a spare bedroom
spare cash
spare parts
spare time

A2 time when you are not working:

I enjoy gardening in my spare time.

(Definition of “spare adjective” from the Cambridge Learner's Dictionary © Cambridge University Press)