Source : Webster's Revised Unabridged Dictionary (1913)

Unkind \Un*kind"\, a. [See {Kin} kindred.]
   Having no race or kindred; childless. [Obs. & R.] --Shak.

Unkind \Un*kind"\, a.
   1. Not kind; contrary to nature, or the law of kind or
      kindred; unnatural. [Obs.] ``Such unkind abominations.''
      --Chaucer.

   2. Wanting in kindness, sympathy, benevolence, gratitude, or
      the like; cruel; harsh; unjust; ungrateful.

            He is unkind that recompenseth not; but he is most
            unkind that forgetteth.               --Sir T.
                                                  Elyot.
      -- {Un*kind"ly}, adv. -- {Un*kind"ness}, n.

Source : WordNet®

unkind
     adj 1: lacking kindness; "a thoughtless and unkind remark"; "the
            unkindest cut of all" [ant: {kind}]
     2: deficient in humane and kindly feelings [syn: {pitiless}]
     3: lacking or showing kindness or compassion or mercy [syn: {cruel}]
     4: used of circumstances (especially weather) that cause
        suffering; "brutal weather"; "northern winters can be
        cruel"; "a cruel world"; "a harsh climate"; "a rigorous
        climate"; "unkind winters" [syn: {brutal}, {cruel}, {harsh},
         {rigorous}]