[from the carnival game which involves quickly and repeatedly hitting
the heads of mechanical moles with a mallet as they pop up from their
holes.]
1. The practice of repeatedly causing spammers' {throwaway account}s
and drop boxes to be terminated.
2. After sense 1 became established in the mid-1990s the term passed
into more generalized use, and now is commonly found in such
combinations as whack-a-mole windows; the obnoxious pop-up
advertisement windows spawned in flocks when you surf to sites like
Angelfire or Lycos.
[glossary]