spare

1 spare /ˈspeɚ/ adjective
sparer; sparest
1 spare
/ˈspeɚ/
adjective
sparer; sparest
Britannica Dictionary definition of SPARE
1 
always used before a noun
a  : kept as something extra that can be used if it is needed
— see also spare tire
b  : available to be used in whatever way you want
c  : not needed by you and available to be shared or given to someone else
2 
: somewhat thin
3 
: simple or plain

going spare

British, informal
: not being used : available for someone to use

go spare

British, informal
: to become very angry or upset
2 spare /ˈspeɚ/ verb
spares; spared; sparing
2 spare
/ˈspeɚ/
verb
spares; spared; sparing
Britannica Dictionary definition of SPARE
[+ object]
1 
a  : to choose not to punish or harm (someone)
b  : to not destroy or harm (something)
2 
: to prevent (someone or something) from experiencing or being affected by something unpleasant, harmful, etc.
3 
: to give (something, such as time, money, etc.) to someone
4 
: to not do or provide (something)
5 
: to use or give out (something) in small amounts — usually used in negative statements

spare someone's blushes

British, informal
: to prevent someone from being embarrassed

spare someone's feelings

: to avoid doing or saying something that will hurt someone emotionally : to avoid upsetting someone

spare (someone) the details

: to not tell someone all the unpleasant or boring details about something

to spare

◊ If you have money, time, energy, etc., to spare, you have more than enough money, time, energy, etc.
3 spare /ˈspeɚ/ noun
plural spares
3 spare
/ˈspeɚ/
noun
plural spares
Britannica Dictionary definition of SPARE
[count]
1 
: something extra that is kept to be used if it is needed
2 
bowling : the achievement of knocking down all 10 pins with the first two balls
— compare 2strike 6