an extra component of a machine or other apparatus
"The mechanic asked me to grab a spare filter from the toolbox before he could finish fixing the engine."
an extra car wheel and tire for a four-wheel vehicle
"I need to stop at the garage to swap my flat front tire for the spare before I can continue driving."
a score in tenpins; knocking down all ten after rolling two balls
"He celebrated loudly after finally getting his first spare at the bowling alley, having knocked down all the pins on his second throw."
The act of sparing; moderation; restraint.
"After years of overworking, she decided to practice a bit of spare in her schedule to finally enjoy some rest."
In plain English: A spare is an extra item kept on hand just in case you need it.
"Please find a spare pen on the desk."
save or relieve from an experience or action
"I'll spare you from having to apologize formally"
give up what is not strictly needed
"he asked if they could spare one of their horses to speed his journey"
use frugally or carefully
"He tries to spare every drop of water during the drought by taking only a shower at night."
To show mercy.
"The judge decided to spare the young thief from prison due to his lack of prior offenses."
To desist; to stop; to refrain.
"Please spare me your long explanations about why you are late."
In plain English: To spare something means to choose not to use it, hurt it, or give it away.
"You could spare me a few minutes to explain how this works."
more than is needed, desired, or required
"trying to lose excess weight"
"found some extra change lying on the dresser"
"yet another book on heraldry might be thought redundant"
"skills made redundant by technological advance"
"sleeping in the spare room"
"supernumerary ornamentation"
"it was supererogatory of her to gloat"
"delete superfluous (or unnecessary) words"
"extra ribs as well as other supernumerary internal parts"
"surplus cheese distributed to the needy"
kept in reserve especially for emergency use
"a reserve supply of food"
"a spare tire"
"spare parts"
lacking embellishment or ornamentation
"a plain hair style"
"unembellished white walls"
"functional architecture featuring stark unornamented concrete"
Scant; not abundant or plentiful.
"His supply of coffee was so spare that we had to ration it strictly among just two cups for the whole morning."
In plain English: Spare means having extra or unused items available when you need them.
"I have a spare ticket if you want to go to the concert with me."
Usage: Use sparingly to describe something that exists in very small amounts, such as spare time or spare resources. This meaning differs from the more common sense of having an extra item available for use when needed.
The word spare comes from Old English spær, which originally meant "sparing" or "scant." It traveled into modern usage to describe something that is not used up or reserved for special occasions.