Refers to a spare part, spare tire, or something kept as a backup. Common in compound nouns like スペアタイヤ (spare tire) and スペアパーツ (spare parts).
There's a spare tire in the car.
Are spare parts for this machine still available?
spare; knocking down all pins on the second throw
Bowling term: when a player knocks down the remaining pins with the second ball of a frame.
He got a spare in the fifth frame.
I have a spare key for my bicycle.
He scored a spare in the final frame and came back to win.
Before the long trip, I prepared a spare battery.
Loanword from English 'spare'.