Source : Webster's Revised Unabridged Dictionary (1913)

Unsparing \Un*spar"ing\, a. [Pref. un- not + sparing, p. pr. of
   spare.]
   1. Not sparing; not parsimonious; liberal; profuse. --Burke.

   2. Not merciful or forgiving. [R.] --Milton. --
      {Un*spar"ing*ly}, adv. -- {Un*spar"ing*ness}, n.