plonk

from WordNet (r) 3.0 (2006)

plonk
    n 1: a cheap wine of inferior quality
    2: the noise of something dropping (as into liquid)
    v 1: set (something or oneself) down with or as if with a noise;
         "He planked the money on the table"; "He planked himself
         into the sofa" [syn: {plank}, {flump}, {plonk}, {plop},
         {plunk}, {plump down}, {plunk down}, {plump}]

from Jargon File (4.4.4, 14 Aug 2003)

plonk
 excl.,vt.

   [Usenet: possibly influenced by British slang `plonk' for cheap booze,
   or `plonker' for someone behaving stupidly (latter is lit. equivalent
   to Yiddish schmuck)] The sound a {newbie} makes as he falls to the
   bottom of a {kill file}. While it originated in the {newsgroup}
   talk.bizarre, this term (usually written "*plonk*") is now (1994)
   widespread on Usenet as a form of public ridicule.

from The Free On-line Dictionary of Computing (8 July 2008)

plonk

   <networking, abuse> (Possibly influenced by British slang
   "plonk" for cheap booze, or "plonker" for someone behaving
   stupidly; usually written "*plonk*") The sound a {newbie}
   makes as he falls to the bottom of a {kill file}.  While this
   term originated in the {Usenet} {newsgroup}
   news:talk.bizarre, by 1994 it was widespread on Usenet and
   mailing lists as a form of public ridicule.

   Another theory is that it is an acronym for "Person with
   Little Or No Knowledge".

   (2002-01-18)

from V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006)

PLONK
       Please Leave Our Newsgroup, Kid (Usenet, slang)