The Collaborative International Dictionary of English v.0.48:

Thrash \Thrash\, Thresh \Thresh\, v. t. [imp. & p. p.
   Thrashed; p. pr. & vb. n. Thrashing.] [OE.
   [thorn]reschen, [thorn]reshen, to beat, AS. [thorn]erscan,
   [thorn]rescan; akin to D. dorschen, OD. derschen, G.
   dreschen, OHG. dreskan, Icel. [thorn]reskja, Sw. tr["o]ska,
   Dan. t[ae]rske, Goth. [thorn]riskan, Lith. traszketi to
   rattle, Russ. treskate to burst, crackle, tresk' a crash,
   OSlav. troska a stroke of lighting. Cf. Thresh.]
   1. To beat out grain from, as straw or husks; to beat the
      straw or husk of (grain) with a flail; to beat off, as the
      kernels of grain; as, to thrash wheat, rye, or oats; to
      thrash over the old straw.
      [1913 Webster]

            The wheat was reaped, thrashed, and winnowed by
            machines.                             --H. Spencer.
      [1913 Webster]

   2. To beat soundly, as with a stick or whip; to drub.
      [1913 Webster] Thrash

The Collaborative International Dictionary of English v.0.48:

Thrashing \Thrash"ing\,
   a. & n. from Thrash, v.
   [1913 Webster]

   Thrashing floor, Threshing-floor, or Threshing floor, a
      floor or area on which grain is beaten out.

   Thrashing machine, a machine for separating grain from the
      straw.
      [1913 Webster]

WordNet (r) 3.0 (2006):

thrashing
    n 1: a sound defeat [syn: thrashing, walloping, debacle,
         drubbing, slaughter, trouncing, whipping]
    2: the act of inflicting corporal punishment with repeated blows
       [syn: beating, thrashing, licking, drubbing,
       lacing, trouncing, whacking]

Moby Thesaurus II by Grady Ward, 1.0:

74 Moby Thesaurus words for "thrashing":
   Waterloo, assault, bastinado, basting, battering, battery, beating,
   belting, buffeting, caning, castigation, chastisement, clubbing,
   collapse, conquering, conquest, corporal punishment, cowhiding,
   crash, cudgeling, deathblow, debacle, defeasance, defeat,
   destruction, discipline, disciplining, downfall, drubbing, failure,
   fall, flagellation, flailing, flogging, fustigation, hammering,
   hiding, horsewhipping, lacing, lambasting, lashing, lathering,
   licking, mastery, mauling, overcoming, overthrow, overturn,
   pasting, pistol-whipping, pounding, punishment, quietus, rawhiding,
   rout, ruin, scourging, shellacking, smash, spanking, strapping,
   stripes, subdual, subduing, subjugation, swingeing, switching,
   tanning, trimming, trouncing, truncheoning, undoing, vanquishment,
   whipping



The Free On-line Dictionary of Computing (30 December 2018):

thrash
thrashing

   To move wildly or violently, without accomplishing anything
   useful.  Paging or swapping systems that are overloaded
   waste most of their time moving data into and out of core
   (rather than performing useful computation) and are therefore
   said to thrash.  Thrashing can also occur in a cache due to
   cache conflict or in a multiprocessor (see ping-pong).

   Someone who keeps changing his mind (especially about what to
   work on next) is said to be thrashing.  A person frantically
   trying to execute too many tasks at once (and not spending
   enough time on any single task) may also be described as
   thrashing.

   Compare multitask.

   [Jargon File]