adware

from Jargon File (4.4.4, 14 Aug 2003)

adware
 n.

   Software which is free to download and use but includes pop-up banner
   ads somewhere. See also {-ware}.

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

adware

   <software> Any kind of {software} which is distributed free of
   charge along with advertisements that are either placed on the
   {web site} from which the software is distributed or displayed
   by the program while it is running.

   {Nagware} might be considered a special case of adware where
   the program tries to persuade the user to buy a license for
   the program itself.

   (2007-11-20)