'Sparer' definitions:

Definition of 'sparer'

noun

Someone who refrains from injuring or destroying

From: GCIDE

Spare \Spare\, a. [Compar. Sparer; superl. Sparest; -- not used in all the senses of the word.] [AS. spaer sparing. Cf. Spare, v. t. ]
1. Scanty; not abundant or plentiful; as, a spare diet. [1913 Webster]
2. Sparing; frugal; parsimonious; chary. [1913 Webster]
He was spare, but discreet of speech. --Carew. [1913 Webster]
3. Being over and above what is necessary, or what must be used or reserved; not wanted, or not used; superfluous; as, I have no spare time. [1913 Webster]
If that no spare clothes he had to give. --Spenser. [1913 Webster]
4. Held in reserve, to be used in an emergency; as, a spare anchor; a spare bed or room. [1913 Webster]
5. Lean; wanting flesh; meager; thin; gaunt. [1913 Webster]
O, give me the spare men, and spare me the great ones. --Shak. [1913 Webster]
6. Slow. [Obs. or prov. Eng.] --Grose. [1913 Webster]

From: GCIDE