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.

Source : WordNet®

unsparing
     adj 1: very generous; "distributed gifts with a lavish hand"; "the
            critics were lavish in their praise"; "a munificent
            gift"; "his father gave him a half-dollar and his
            mother a quarter and he thought them munificent";
            "prodigal praise"; "unsparing generosity"; "his
            unstinted devotion"; "called for unstinting aid to
            Britain" [syn: {lavish}, {munificent}, {overgenerous},
             {prodigal}, {too-generous}, {unstinted}, {unstinting}]
     2: not forbearing; ruthless; "an unsparing critic"