1. A replacement, especially a tire, reserved for future need.
2. Sports
a. The act of knocking down all ten pins with two successive rolls of a bowling ball.
b. The score so made.
Idiom:
to spare
In addition to what is needed: We paid our bills and had money to spare.
[Middle English sparen, from Old English sparian.]
sparely adv.
spareness n.
sparer n.
spare /spr/ v. [T] spared, sparing, spares1 to save or prevent s.o. from harm: The enemy soldier didnt shoot me; he spared me (or) he spared my life.2 to keep s.o. from having to do s.t.: If you pick up the kids at school, youll spare me the trouble.3 to have enough to give or share: Can you spare a few dollars to lend her?4s.t. to spare: more, left over: We have enough hamburgers for everyone, and two to spare. adj.1 unused, extra: a spare room for a guest2sparer, sparest thin, lean: a spare man who doesnt eat much n. (in bowling) the act of causing all the pins to fall with two rolls of the ball
r/ v. [T] spared, sparing, spares 1 to save or prevent s.o. from harm: The enemy soldier didnt shoot me; he spared me (or) he spared my life. 2 to keep s.o. from having to do s.t.: If you pick up the kids at school, youll spare me the trouble. 3 to have enough to give or share: Can you spare a few dollars to lend her? 4 s.t. to spare: more, left over: We have enough hamburgers for everyone, and two to spare. 
adj. 1 unused, extra: a spare room for a guest 2 sparer, sparest thin, lean: a spare man who doesnt eat much 
ly adv.