The Collaborative International Dictionary of English v.0.48:

knock-down-and-drag-out \knock-down-and-drag-out\,
knockdown-dragout \knockdown-dragout\adj.
   marked by extreme violence; -- of fights; also used
   metaphorically of fierce contests; as, a
   knock-down-and-drag-out fight; a knockdown-dragout
   competition for the browser market.

   Syn: ferocious, fierce, knockdown-dragout, tearing.
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

knockdown-dragout
    adj 1: extremely violent; "a knock-down-and-drag-out fight"
           [syn: knockdown-dragout, knock-down-and-drag-out]