Source : Webster's Revised Unabridged Dictionary (1913)

Barbarous \Bar"ba*rous\, a. [L. barbarus, Gr. ?, strange,
   foreign; later, slavish, rude, ignorant; akin to L. balbus
   stammering, Skr. barbara stammering, outlandish. Cf. {Brave},
   a.]
   1. Being in the state of a barbarian; uncivilized; rude;
      peopled with barbarians; as, a barbarous people; a
      barbarous country.

   2. Foreign; adapted to a barbaric taste. [Obs.]

            Barbarous gold.                       --Dryden.

   3. Cruel; ferocious; inhuman; merciless.

            By their barbarous usage he died within a few days,
            to the grief of all that knew him.    --Clarendon.

   4. Contrary to the pure idioms of a language.

            A barbarous expression                --G. Campbell.

   Syn: Uncivilized; unlettered; uncultivated; untutored;
        ignorant; merciless; brutal. See {Ferocious}.

Source : WordNet®

barbarous
     adj 1: (of persons or their actions) able or disposed to inflict
            pain or suffering; "a barbarous crime"; "brutal
            beatings"; "cruel tortures"; "Stalin's roughshod
            treatment of the kulaks"; "a savage slap"; "vicious
            kicks" [syn: {brutal}, {cruel}, {fell}, {roughshod}, {savage},
             {vicious}]
     2: primitive in customs and culture