The Collaborative International Dictionary of English v.0.48:

Slash \Slash\, v. t. [imp. & p. p. Slashed; p. pr. & vb. n.
   Slashing.] [OE. slaschen, of uncertain origin; cf. OF.
   esclachier to break, esclechier, esclichier, to break, and E.
   slate, slice, slit, v. t.]
   1. To cut by striking violently and at random; to cut in long
      slits.
      [1913 Webster]

   2. To lash; to ply the whip to. [R.] --King.
      [1913 Webster]

   3. To crack or snap, as a whip. [R.] --Dr. H. More.
      [1913 Webster]

WordNet (r) 3.0 (2006):

slashing
    adj 1: as if striking with slashing blows; "his slashing demon-
           ridden cadenza"

Moby Thesaurus II by Grady Ward, 1.0:

79 Moby Thesaurus words for "slashing":
   abscission, acid, amputation, biting, burr, butchering, chiseling,
   chopping, cleavage, corrosive, cross-hatching, cutting, demitint,
   dichotomy, driving, effective, engravement, engraving, enucleation,
   etch, etching, excision, fission, forceful, forcible,
   gem-engraving, glass-cutting, glyptic, graving, gutsy, half tint,
   hatching, imperative, impressive, incision, incisive, inscript,
   inscription, laceration, line, lining, marking, mordant,
   mutilation, nervous, penetrating, piercing, poignant, powerful,
   punchy, rending, resection, ripping, scission, score, scoring,
   scratch, scratching, section, sensational, severance, sinewed,
   sinewy, slash, slicing, splitting, stipple, stippling, striking,
   strong, surgery, tearing, telling, tint, tooling, trenchant,
   type-cutting, vigorous, vital