The Collaborative International Dictionary of English v.0.48:

Barbarous \Bar"ba*rous\, a. [L. barbarus, Gr. ba`rbaros,
   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.
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   2. Foreign; adapted to a barbaric taste. [Obs.]
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            Barbarous gold.                       --Dryden.
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   3. Cruel; ferocious; inhuman; merciless.
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            By their barbarous usage he died within a few days,
            to the grief of all that knew him.    --Clarendon.
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   4. Contrary to the pure idioms of a language.
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            A barbarous expression                --G. Campbell.
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   Syn: Uncivilized; unlettered; uncultivated; untutored;
        ignorant; merciless; brutal. See Ferocious.
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WordNet (r) 3.0 (2006):

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: barbarous, brutal, cruel, fell,
           roughshod, savage, vicious]
    2: primitive in customs and culture